When you have a strong starting rotation and play in a pitcher’s park, it is a reasonable expectation that you will defend your home field in the playoffs. The Giants, so far, haven’t been able to do that and the problems start with the starters.

Bruce Bochy has had three home playoff games so far, and his starter has lasted five innings or less in each of them, all losses. Matt Cain went five full innings in game one of the Division Series and gave up three runs on two homers. Madison Bumgarner pitched the next night, but only for 4 1/3 innings, allowing seven hits and four runs. That worked out in the end for the Giants, as they won three road games in Cinncinati to advance to the NLCS.

But last night, things got out of hand quickly for the Giants and again it was the starter, Bumgarner, who put them behind the eight ball. His line was 3 2/3 IP, 8 hits and 6 ER as he left in the fourth inning where the Cardinal bats struck quickly. The Giants countered with four runs in the bottom of the inning to chase St. Louis starter Lancy Lynn, but it wasn’t enough.

Today the Giants turn to Ryan Vogelsong, who struggled in August and September but has put together four straight good starts, including one in the Division Series against the Reds. Vogelsong was one of the league leaders in ERA before his rough stretch late in the season. His good outings to finish the regular season came against the Dodgers on the last day of the season and twice against the Padres.

The Giants proved they can win on the road in the playoffs, but Bochy hardly wanted to get into an 0-1 hole after climbing all the way back against the Reds to advance. He will need to have a sharp Vogelsong tonight to avoid going to St. Louis with his back to the wall again.

Even a sharp Vogelsong could take his lumps against these hot-hitting Cardinals, however. With Daniel Descalso and Pete Kozma swinging hot bats from the bottom of the order, St. Louis has an American League-style lineup that doesn’t have a weak spot until you get to the pitcher. And Carlos Beltran is scorching hot in the middle of the order, as he always is in the post season.

One of the things that is giving the Giants trouble at home is that they are unable to hit for power in their pitcher’s park, but their opponents are launching home runs with regularity. Beltran, David Freese, Ryan Ludwick, Brandon Phillips and Jay Bruce have all homered in AT&T Park this October. The Giants have countered with one, from Buster Posey in game one of the Division Series.

In 2012 the Giants hit just 31 home runs in their home ballpark all season. That works for regular season games when your pitching can shut down the opponents with regularity. In the post season, when you’re playing the hottest lineups and pitching staffs that can put up zeroes, it is a problem for the Giants. Bochy’s bullpen was able to restore order during the regular season, but last night, the Cardinals’ relievers were equal to the task. The score remained 6-4 until the bitter end.

Vogelsong gets the most important start of his career tonight and the Cardinals are in a groove. Starter Chris Carpenter is always tough in the post season. It is a daunting task for the Giants. But they need to get it done at home. Coming back from 0-2 in the playoffs isn’t something they want to try to do twice in one post season.