With Adam Wainwright taking the mound, though, their chances to avoid a third consecutive loss figure to be good.
The Cardinals (29-25) have lost three of four after a 6-5 defeat in the opener of this four-game series Thursday. They've dropped back-to-back games six times this year, but have outscored opponents 31-16 in winning the next contest.
Wainwright (8-2, 1.67), the major leagues' ERA leader, stopped two of those two-game skids and is looking to become the first nine-game winner in the NL. The right-hander has gone 3-0 with a 0.87 ERA in his last four starts, completing at least eight innings in three of them.
He matched a career best with 12 strikeouts over eight innings of a 4-0 victory at Cincinnati on Sunday. It was Wainwright's sixth scoreless outing of the season, matching his total in 34 starts last year.
"I've never felt like this," Wainwright said. "That's part of the evolution of me. I expected to get better as I got older, and a little wiser. Now that I'm over 30 years old, I don't think there's any reason for me to start to decline. I think I should still try to get better and expect to get better."
Wainwright is 4-4 with a 2.70 ERA in 10 career appearances versus the Giants, but has won three straight starts against them with a 1.57 ERA.
San Francisco (35-19) has won seven of eight after getting homers from Michael Morse and Pablo Sandoval on Thursday. Sandoval has five home runs and 13 RBIs during an eight-game hitting streak and he's 5 for 13 against Wainwright.
"We're just playing," said Morse, batting .383 with two home runs and 13 RBIs over the last 13 contests. "The mentality we have and the fun we're having, I think winning is contagious and we love to win."
Madison Bumgarner (6-3, 3.15) comes in riding a hot stretch of his own, going 4-0 with a 2.53 ERA in five starts this month with 38 strikeouts in 32 innings. However, the left-hander has posted a 5.59 ERA during a three-start losing streak against the Cardinals.
Each team rested a top hitter Thursday for precautionary reasons. St. Louis' Matt Adams sat for the second straight game due to a tight left calf, while San Francisco's Buster Posey didn't play after a back issue flared up. Posey, who missed two games last week with nerve irritation, has gone 3 for 32 over his last nine games.
"We'd like to get this thing taken care of," manager Bruce Bochy told the team's official website.
Matt Carpenter is batting .360 during an 11-game hitting streak after singling twice Thursday. He's 17 for 34 in 11 career matchups with San Francisco.
Wainwright has gone 6-0 with a 1.57 ERA in his last eight regular-season home starts dating to Sept. 7, while Bumgarner is 3-1 with a 1.88 ERA in six road outings this season. He lost his last game at Busch Stadium, however, allowing five runs over six innings of a 7-1 defeat June 1.