St. Louis made three errors in a game for the second time this week with the most important coming in the sixth inning: Third baseman David Freese’s errant throw on

pinch-hitter Aubrey Huff’s two-out grounder allowed Brandon Belt to score the go-ahead run.

First baseman Lance Berkman also made an error in the second inning to help lead to Crawford’s two-run single. Three of the five runs scored off Adam Wainwright (2-5) were unearned.

Cain (3-2) has been plagued by poor run support for his entire career with the Giants scoring a major league-low 3.89 runs per game for him since his first big league season in 2006.

But with help from the Cardinals they managed to score five runs with Cain in the game on Thursday to make up for his rough start that included Matt Holliday’s two-run homer in the third inning. San Francisco had its highest-scoring home game of the season.

Santiago Casilla pitched the ninth for his ninth save in 10 chances.

Cain came into the game with the second best ERA at home in the majors this season, having allowed four runs in 33 innings for a 1.09 mark. He allowed as many runs in the first three innings against the Cardinals as he had in his previous four starts here.

He

allowed sacrifice flies by Holliday and Freese in the first inning and Holliday’s two-run homer in the third to fall behind 4-3. Cain retired 10 of the final 11 batters he faced. He allowed four runs and eight hits in six innings.

Crawford doubled and scored on Buster Posey’s single in the first and then hit his two-run single in the second for the Giants, ending a string of 16 straight games without driving in a run.

Cain ended up on the winning side when the Giants got two runs in the bottom of the sixth after Angel Pagan led off the inning with a single and went to third on Belt’s double.

Emmanuel Burriss tied the game with a sacrifice fly. It looked like the game would stay that way when reliever Victor Marte got Huff to hit a grounder to third with two outs. But Freese’s throw to first was high, allowing Belt to score from second on the error.

Wainwright allowed five runs — two earned — and eight hits in 5 2-3 innings and is winless in five career starts against the Giants.

San Francisco added two runs in the seventh off Kyle McClellan on Belt’s RBI double and Charlie Culberson’s groundout. McClellan left the game with a sore right elbow.

Yadier Molina hit a solo homer in the eighth for St. Louis for the first run of the season off reliever Sergio Romo.

NOTES: Cardinals OF Carlos Beltran (right knee) did not start for a fourth straight game. He popped out as a pinch-hitter in the ninth. … Cardinals OF Allen Craig sat after tweaking his left hamstring Wednesday. … Giants 3B Joaquin Arias missed his second straight game after being hit in the left forearm Tuesday. … Lance Lynn (6-1) takes the mound for the Cardinals when they open a three-game series in Los Angeles against Ted Lilly (5-0) and the Dodgers. … Former Oakland ace Barry Zito, who is 1-4 with a 7.24 ERA in five starts against his former team, starts the series opener of the first Bay Bridge series for the Giants against Jarrod Parker.

The Giants suddenly have a huge void in their bullpen with the likely loss of Brian Wilson for the season. But unlike when they lost Buster Posey in 2011, the club isn’t lacking for candidates ready, willing and able to step in for the club’s fallen closer.

In a 4-3 victory over the Pittsburgh Pirates on Saturday night at AT&T Park, relievers Santiago Casilla and Javier Lopez made an immediate case they might be able to fill the void.

After Barry Zito pitched seven solid innings and departed a 3-3 game, Casilla and Lopez held the Pirates scoreless over the next two innings to set up the Giants’ third straight win.

A bases-loaded, none-out throwing error in the bottom of the ninth brought home the winning run.

Casilla pitched 12/3 innings of one-hit ball, and Lopez (1-0) got the final out in the top of the ninth by striking out Alex Presley with the potential go-ahead run on second. It was some much-needed balm after a stunning jolt of bad news. Wilson faces likely season-ending surgery after an MRI revealed “structural issues” in his right elbow.

“We certainly feel for Brian,” Lopez said. “But we did have a little taste of this in September when they had to shut Brian down for a little while. So I think we can do it.

“Obviously, I think everybody believes in the skills and talents that we have (in the bullpen), and we complement each other so well.”

Sergio Romo didn’t pitch Saturday, but he echoed

Lopez’s sentiments although he said that if Wilson is done for the season, it’s a horrible loss personally.

“He’s our closer, he’s our captain, he’s our leader in the bullpen,” Romo said. “The last 4-5 years, he’s probably been the best closer in the game, so it hurts a lot. But I personally feel any one of us can handle any situation (manager Bruce) Bochy puts us in.”

Wilson pitched just twice after Aug. 15 last year, but Bochy thought the bullpen more than held its own.

“This bullpen’s going to have to tighten things up with Wilson gone, and tonight we did it,” Bochy said.

The Giants also continued to score the necessary runs to enhance their chances of winning. They’ve now scored at least four runs in every game. On this night, they had to stage two comebacks after falling behind 2-0 in the first inning and 3-2 in the fifth.

In the ninth, they cobbled together an impressive rally. Emmanuel Burriss, who had an RBI single earlier in the game, started things off with a sharp first-pitch single to right. Pinch-hitter Ryan Theriot then shot a single past first baseman Casey McGehee to put runners at first and third. Angel Pagan was intentionally walked to loaded the bases, setting up things for Melky Cabrera.

Cabrera, who went hitless for the first time this season (he did draw a walk), worked the count to 3-2 before hitting a grounder to shortstop Clint Barmes with the infield in. Barmes appeared to have an easy force out of Burriss at home plate but threw low, and the ball skipped past catcher Rod Barajas as Burriss scored.

The Giants are now 4-4 after starting the season 0-3. So there was still a somewhat upbeat mood despite the shocking news about Wilson.

“I’ve played with Brian since low A-ball in 2004,” said outfielder Nate Schierholtz, who continued his hot hitting with an RBI triple and a double. “Anytime a good friend goes down, it’s not easy. It’s a bummer. But he’ll get through it. And we have to move on and play our game.”

As for Zito, he wasn’t as sharp as he was in his stunning four-hit, no-walk shutout in Colorado on Monday, but after a shaky first inning, he allowed just three hits and an unearned run the rest of his stint.

Zito, too, was happy to see the relievers step up without Wilson.

“This bullpen runs deep, and it has for a few years,” Zito said. “Roles aren’t defined yet, but I won’t be surprised if we’re able to come out of this OK.”

Eight games into the 2012 season, the Giants have suffered a potentially devastating injury. Closer Brian Wilson is facing likely elbow surgery and might be lost for the season.

An MRI on Friday night revealed that Wilson has “structural issues” with the ligament in his right elbow, manager Bruce Bochy said Saturday before the Giants’ 4-3 victory over the Pittsburgh Pirates at AT&T Park. Wilson has been placed on the 15-day disabled list, but he’s probably going to be out a lot longer.

After a 32-pitch inning against Colorado on Thursday in which he struggled to get the save during a 4-2 Giants’ win, Wilson complained of elbow stiffness Friday. Subsequent tests revealed structural damage, to what degree the club was not yet prepared to say.

Bochy and trainer Dave Groeschner said Wilson would be examined by team orthopedist Dr. Ken Akizuki and that calls then would be made to set up second and third opinions, including from noted Pensacola, Fla., elbow surgeon Dr. James Andrews, before making a final determination about surgery.

The manager did not sound optimistic.

“After the tests (Friday), it doesn’t look very good right now,” Bochy said. “He’ll get a couple more opinions, but he’s likely facing surgery, to be honest.”

There have been questions about Wilson’s health since he blew a save in a 5-4 walk-off loss to Atlanta on Aug. 15. Wilson was examined by Andrews two days later and placed on the disabled list Aug.

21 with inflammation in the elbow. He was reinstated Sept. 18 but appeared in just two games before being shut down for the remainder of the season.

During spring training, Wilson said the late-season shutdown was done for precautionary reasons and that there were no issues with the elbow.

“I am healthy, and I’m doing everything I can to make sure everyone is aware of that,” he said March 26. “(The elbow) wasn’t a concern for me.”

Wilson, who turned 30 last month, made six appearances in spring training, throwing 51/3 innings with no earned runs allowed, two walks and eight strikeouts.

He made his regular-season debut Wednesday, pitching the eighth inning of a 17-8 loss in Denver. He gave up a run on one hit and one walk, throwing 24 pitches.

Wilson’s second outing of the season was even more difficult. He loaded the bases and walked in a run before preserving a 4-2 victory. At one point, Bochy and Groeschner, along with catcher Buster Posey, came out to check on Wilson. He took a warm-up pitch and finished the game, and afterward, Bochy said Wilson had tweaked his left ankle. His velocity declined noticeably during the inning.

Groeschner said the elbow issue became apparent Friday afternoon when Wilson went through his pregame routine.

“Even though he was off, he still had to throw and prepare,” the trainer said. “That’s when he came and talked to us.”

Said Bochy: “I feel for Willie. He’s worked hard with rehab, and he’d come a long way. We checked off every box with him, back-to-back days, everything. I think he was all set to go, and then this happens, so it’s a disappointing day for Willie personally, and then obviously the team.”

Wilson was not available for comment, but Bochy spoke with him.

“I’m sure he’s disappointed with what’s happened, and we all feel terrible,” the manager said. “But he said, ‘Hey, I’ll be back to help you guys.’ “

If Wilson requires Tommy John ligament replacement surgery, however, his season will almost surely be over. It would be his second such surgery — he had the procedure in 2003 while attending LSU. The Giants nonetheless drafted him in the 24th round that year.

Wilson has 171 career saves, including 36 last season. He led the majors with 48 saves in 2010 and had six more in the postseason, including closing out all three series-clinching wins en route to the Giants’ first World Series victory in San Francisco.

Bochy said Ryan Vogelsong, who was scheduled to come off the disabled list Sunday to make his first start of the season, would replace Wilson on the roster.

As for how Wilson would be replaced in the bullpen, Bochy said it would be a closer by committee for the time being.

“It’ll be similar to last year when Willie was out,” he said. “We’ll use everybody, go with the hot hand. (Santiago) Casilla may be saving some games. (Sergio) Romo and (Javier) Lopez, we think we’re in good hands there. That’s the game plan right now.”

Wilson could be joining a long list of pitchers throughout baseball who have suffered elbow injuries early in the season. Cincinnati closer Ryan Madson underwent Tommy John surgery earlier this week, as did the A’s Joey Devine and the Angels’ Michael Kohn.

Kansas City closer Joakim Soria had the surgery April 3, and Minnesota right-hander Scott Baker is scheduled for season-ending surgery to repair the flexor pronator tendon in his elbow. The Twins released right-hander Joel Zumaya after he injured his elbow in his first spring training bullpen session.

Matt Cain might just end up being worth every penny.

The highest-paid right-hander in baseball history flirted with on-field history Friday, taking a perfect game deep into a 5-0 victory over the Pittsburgh Pirates. Cain retired the first 17 hitters he faced in the Giants’ home opener and finished with a one-hitter.

Pirates pitcher James McDonald scuttled Cain’s bid for the first perfect game in Giants history with a sixth-inning single.

“I was definitely aware of it,” Cain said of the perfect game bid. “He put a good swing on it. He did his job.”

Cain did his the rest of the way. McDonald was the first and only Pirates base runner, but he hit his liner to left field just hard enough to keep Cain from accomplishing a lifelong goal of throwing a perfect game.

“I’m always kind of conscious of it,” he said. “I’ve never had one.”

Cain has had three one-hitters in his Giants career. This might have been his best — he struck out 11, one short of his career high.

“We’ve all seen him locked in like this, but this was as good as he’s been,” manager Bruce Bochy said. “He had all his pitches working.”

Cain was given plenty of run support for a second straight start, and Buster Posey made sure some of it came in dramatic fashion.

In his first official at-bat at AT&T Park since the devastating home-plate collision last May 25, Posey doubled off the center-field wall to bring Melky Cabrera home in the first

inning.

Posey scored a batter later on a single by Aubrey Huff.

“Buster smashed that ball,” Bochy said. “That helps guys settle down. They’re hyped up and they want to put on a show for the fans.”

The middle of the order produced another run in the sixth when Pablo Sandoval doubled and scored on Nate Schierholtz’s single.

“They’re just making stuff happen,” Cain said. “Melky has been swinging a hot bat, and he’s been doing that since spring training. You get Pablo and Buster behind those guys — that’s going to be fun for us.

“We’re excited about those guys.”

The Giants will have an additional reason to be excited if Huff can continue extending the heart of the order. He capped the scoring in the eighth, hitting a two-run homer on a 95 mph offering from Pirates closer Joel Hanrahan.

“I cheated as much as I’ve ever cheated in my life and got pretty lucky, to be honest with you,” Huff said.

Lucky or not, Huff already is ahead of the dismal pace he set at the plate last season. He didn’t hit his first homer at AT&T Park until his 13th home game in 2011, when he hit just .246 with 12 homers.

“I’ve played this game long enough to know that you’re going to have some good years and some bad years,” he said. “Last year was a terrible year.”

It was that way for the whole offense, but the early signs this season are more than encouraging. The streak of seven straight games scoring four or more runs is the Giants’ longest since 2003.

“I think it’s just a different type of offense that we’ve got now,” Huff said. “It’s a different brand of baseball, no doubt.”

The Giants’ bread and butter, though, remains the same. A starting staff that was shelled in the season’s opening series is back to its old tricks, throwing two complete-game shutouts in the last four games. Barry Zito blanked the Colorado Rockies on four hits Monday. Madison Bumgarner threw 51/3 innings of no-hit ball against the Rockies Thursday in a 4-2 Giants win.

Cain’s shutout was the fifth of his career, but he came up just short of reaching his elusive goal.

“You get to the fifth or sixth inning and it’s hard not to think about (a perfect game),” Posey said. “You definitely felt like we had a shot.”