The Giants might have staged one of their most spirited comebacks of the season to force extra innings, but they ended up losing a piece of their soul Wednesday night.

Buster Posey, their catcher and cleanup hitter, sustained what appeared to be a significant injury to his left ankle in a home-plate collision in the 12th inning. Florida's Scott Cousins barreled into Posey while scoring the tiebreaking run as the Giants lost 7-6 to the Marlins.

Manager Bruce Bochy said Posey was going in for X-rays shortly after the game.

"We haven't had a chance to look at it," Bochy said. "The catcher is vulnerable out there; that's the toughest play in baseball with the runner bearing down.

"You hate to see it. He's our guy behind the plate. When I see him laying there, it's not a good feeling for me, certainly not for him, his teammates, anybody. We're hoping; we're hoping he's OK."

(For further details, visit our Giants blog.)

The remnants of the crowd went silent as Posey squirmed on the ground. He had barely received the throw from Nate Schierholtz, who had caught Emilio Bonifacio's sacrifice fly in right field, when Cousins came in hard and high. Posey's left ankle appeared to grab in the dirt while the rest of his body went flying.

Trainers carried him off the field as he put no weight on his left foot.

Giants second baseman Freddy Sanchez said he thought it was a clean play by Cousins.

"It's just unfortunate it happened," he said. "In that moment you're just praying, just praying it's nothing too serious."

The play was a stark contrast to what had been an inspiring, four-run comeback in the ninth inning. Aubrey Huff, who had broken his bat in frustration while striking out in the fifth inning, hit a two-strike, two-out, two-run single off Leo Nuñez -- who had been 18 for 18 in save chances -- to tie it.

Until then, it appeared the Giants would go down in another offensively stymied performance. It was a one-run game when Bochy allowed left-hander Javier Lopez to face Mike Stanton in the top of the ninth. The right-handed slugger hit a three-run double that gave the Marlins a 6-2 lead and began emptying the sellout crowd.

Bochy might have stayed with Lopez too long, deepening a deficit that the Giants managed to overcome when a series of bloops led to their tying rally.

But any angst not directed at the Giants' lack of offense is probably misplaced. The longer it takes them to find an offensive identity, the more likely it becomes that this is who they are, a collection of parts with no drive train.

Huff has acknowledged he is a slow starter, but June is just around the corner, and the Giants are still waiting for some production from their first baseman and No. 3 hitter.

He does share the team lead in RBIs with Posey (21), but that's no mark of pride when you play for the lowest-scoring team in the National League.

An offensive vacuum at first base is a huge part of the problem. Entering Wednesday, the Giants' first basemen ranked 28th among the 30 major league teams in average (.209), runs (15) and RBIs (14).

A year ago in May, Huff nearly had that many RBIs by himself, driving in 13 runs to go with a .330 average and four home runs during the month.

The Giants' lack of offense doomed Madison Bumgarner, who remained 1-6 despite posting a quality start and allowing the tying run to score on a ground ball with the infield in.

Bumgarner was a bit unlucky in a two-run first inning, as the Marlins strung together four singles -- two of them bloops -- and Stanton's line double rocketed just over third baseman Miguel Tejada's reach.

Tejada's single started a tying, two-run rally in the third. Andres Torres doubled in a run and the Giants had the makings of a big inning when Sanchez's single put runners at the corners with one out.

Huff struck out on a pitch in the dirt, though, and the Marlins had Sanchez hung up on the basepaths. But Sanchez did a good job of prolonging the rundown, Torres dashed for home and Florida shortstop Hanley Ramirez threw too late and too high to the plate.

Torres was credited with an official steal of home, the second Giant to do so this season; Aaron Rowand pulled off the feat on a delayed steal April 28 at Pittsburgh.

Posey wasn't the only injury issue for the Giants. Shortstop Mike Fontenot tweaked his groin as he ran out a ground ball in the fourth inning; Manny Burriss replaced him to begin the fifth. The club already was playing a man short after an MRI exam showed that pinch runner Darren Ford sprained his left ankle.

For more on the Giants, see Andrew Baggarly's Extra Baggs blog at blogs.mercurynews.com/extrabaggs.