But if San Francisco is to make it back to the World Series for a second time in three years, the team must win at AT&T Park at least once this series against the wild-card Cardinals.
Game 2 will be Monday night with San Francisco's Ryan Vogelsong taking on St. Louis' Chris Carpenter.
Playing at home has usually been a big advantage for the Giants, who excel with the nightly sellouts and spacious dimensions that help the pitching staff. San Francisco had a 48-33 record at AT&T Park during the regular season and won five of seven postseason home games on the way to the World Series title two years ago.
That hasn't been the case this October as the Giants have been outscored 20-6 in the three home games. The common theme so far has been subpar starting pitching with Bumgarner the main culprit. After going 2-0 with a 2.18 ERA as a rookie in the postseason two years ago, Bumgarner hasn't made it through five innings in either start this year.
"You have to try to find a way, which I wasn't able to do," Bumgarner said. "You just have to keep battling, keep trying to find a way to get the ball where it's supposed to go."
Bumgarner looked in good form at the start, needing just 11 pitches to get through a perfect first inning. But nothing was easy after that.
Yadier Molina lined a single on an 0-2 pitch with one out in the second. David Freese then drove a 3-2 pitch over the wall in left-center to give the Cardinals a 2-0 lead.
Bumgarner then couldn't make it out of the fourth. Daniel Descalso doubled and scored on Pete Kozma's double. Jon Jay added a two-out RBI single and Beltran ended Bumgarner's night with the homer. That marked the first time all year that Bumgarner allowed two homers in a home game and gave him an 11.25 ERA in the postseason.
"I haven't had a lot of life on the ball," Bumgarner said. "In cases where your stuff might not be as sharp you have to try to find a way to get it where it's supposed to go. I'm just missing over the plate a little bit."
Even a strong night from Tim Lincecum and the bullpen couldn't overcome Bumgarner's rough outing. Five Giants relievers combined for 5 1-3 hitless innings with Lincecum throwing two.
The two-time NL Cy Young Award winner had been demoted to the bullpen so far in the playoffs after a rough regular season. He has allowed just one run in 8 1-3 innings so far and gives Bochy an option if he decides not to give the struggling Bumgarner another start.
No Giants starter has made it through the sixth inning so far this postseason.
"If we avoid bumps early I feel like we'll be all right," Lincecum said. "It's not ideal when our starters do what they're doing right now."
The Giants bats woke up in the fourth inning when RBI hits by Brandon Belt and Brandon Crawford and a two-run triple by Gregor Blanco cut the deficit to 6-4. The rally ended when second baseman Daniel Descalso made a diving stop of Angel Pagan's grounder up the middle with runners on first and third.
"He made a great play," Pagan said. "You have to give him credit. I just did my best. He threw a very nice sinker down in the zone that I put in play. I was just hoping it would go through so we could get a run at least."
But they managed only two hits in 5 1-3 innings against the Cardinals bullpen and find themselves in a 1-0 series hole.
Madison Bumgarner allowed two homers and got knocked out early for the second time this postseason and the Giants once again got off to a bad start to a series at home, losing Game 1 of the NL championship series 6-4 to the St. Louis Cardinals on Sunday night.