St. Louis second baseman Kolten Wong hit a walk-off home run to give the Cardinals a 5-4 victory Sunday night over the San Francisco Giants to even the National League Championship Series at one game each.

The Giants had tied the score at 4-4 in the top of the ninth on a wild pitch by St. Louis reliever Trevor Rosenthal but Wong's lead-off blast to right off Sergio Romo in the bottom of the inning to win the game. The NLCS heads to California for Game 3 on Tuesday.

"I knew I hit the ball hard, but I also hit it low and I didn't know if it was going out or not," Wong told reporters.

St. Louis struggled to hit home runs in the regular season -- only twice in 162 games hitting three or more homers in a game -- but four of their five runs came off homers Sunday courtesy of solo shots from Matt Carpenter, Oscar Taveras, Matt Adams and Wong.

The Giants did not have a home run on Sunday, though they outhit the Cardinals 10-8 overall.

The Cards' victory was tempered by the loss of All-Star catcher Yadier Molina, who left the game after injuring an oblique abdominal muscle batting in the seventh.

St. Louis manager Mike Matheny declined to speculate on the chances of Molina being available for the remainder of the series but if the player is replaced on the roster he cannot return for the World Series should the Cardinals get that far.

"It didn't look real good," Matheny said.

Matheny said it had only been a matter of time before his team turned their home run struggles around.

"We've just continued to preach to the guys to stay with the right approach and put a good swing on the pitch.

"Kolten has great bat speed and so does Matt Adams. It's great timing for us to bust out with some power."

San Francisco manager Bruce Bochy sounded reasonably satisfied to return home with the best-of-seven series tied.

"You come in here and get the first game, you want to get greedy and get the second one," he said. "We were close to doing it but this isn't going to be easy. It's going to be a hard-fought series."

Both managers might have concerns over their bullpens, perhaps more so Bochy. San Francisco used five relievers after starter Jake Peavy lasted just four innings, giving up four hits and two runs.