Facing the surging San Diego Padres may not help.
Lackey attempts to bounce back from one of the worst performances of his 12-year career Thursday night, when the Cardinals try to prevent the Padres from winning a season-high sixth straight.
St. Louis (63-56) is two games behind Milwaukee for the NL Central lead and one-half game ahead of San Francisco in the race for the second wild-card spot.
Lackey (1-1, 8.25 ERA) will try to help begin creating some breathing room in the opener of this four-game set after the Cardinals concluded a 2-4 road trip with Wednesday's 5-2 win over Miami.
The right-hander, who was acquired from Boston before the July 31 non-waiver trade deadline, looked capable of making a big difference in his Cardinals debut Aug. 3. He yielded two runs in seven innings of a 3-2 win over the Brewers.
He followed that up six days later by giving up a season highs of nine runs and 13 hits - three homers - in five innings of a 10-3 loss at Baltimore.
"For the most part, I got my butt kicked," Lackey told MLB's official website. "I didn't execute enough pitches. I didn't pitch well enough. ... I'm OK with not having more American League starts."
Now, he's facing the Padres (57-62) for the first time since allowing one run in eight innings of a 4-1 win July 2, 2013.
San Diego has matched its season-high five-game winning streak and won 11 of 14, a stretch that started when it took of three at home against St. Louis at the end of July.
The Padres are averaging 4.6 runs and batting .276 during that 14-game stretch, huge improvements over their 3.3 and .225 season marks.
Rookie Rymer Liriano hit a two-run shot for his first career homer in just his third game and Jedd Gyorko went 4 for 4 in San Diego's 5-3 win over Colorado on Wednesday.
"We know that he's got the raw power," manager Bud Black said of Liriano, who hit 14 homers with 66 RBIs in the minors this year.
Although he's tied for the most losses in baseball, Eric Stults (5-13, 4.76 ERA) has been much better lately. The left-hander has won back-to-back starts for the Padres, yielding two runs - one earned - in 12 2-3 innings.
He was terrific in earning his first road win of the year Saturday, allowing one run and seven hits with six strikeouts over 6 1-3 innings of a 2-1 victory at Pittsburgh. He had been 0-9 with a 5.37 ERA over his previous 12 away starts.
"It's nice to just have a win," Stults said. "This year has been a little frustrating."
Stults was a 3-2 loser in his only visit to St. Louis on July 21, 2013, giving up three runs in six innings.
San Diego is expected to put Yonder Alonso on the disabled list with a wrist injury, while Yangervis Solarte's status is unclear after he left in the seventh Wednesday with a strained muscle in his left side.
Solarte went 5 for 12 with a homer and three RBIs against the Cardinals last month.
St. Louis' Matt Carpenter had four hits in that series, and owns a career .405 average in 13 career meetings with San Diego.