The Braves lost their second in a row and seventh in 10 games on Monday in Florida.
Jackson, who began the season with the Chicago White Sox, came to the Cardinals in a trade deadline deal and has been solid in 10 starts. He's won five of seven decisions in the NL, including three in a row over five starts since Aug. 20.
He was a 3-2 winner at Pittsburgh in his most recent outing Sept. 14, allowing two earned runs and walking none with five strikeouts.
The 28-year-old, born in what was then West Germany, is 60-60 in 120 career decisions over 200 big-league appearances - but he's never faced the Mets.
New York counters with right-hander Mike Pelfrey, who's dropped off from 15 wins last season. The former first-round draft pick is winless in four starts since Aug. 24, when he downed Philadelphia, 7-4 with six innings of three-run ball.
He's 0-2 since, including a tough-luck 2-0 loss to Washington in his last start Sept. 14, when he allowed two unearned runs in seven innings.
Pelfrey is 2-0 with a save in three career meetings with St. Louis, posting a stingy 1.20 earned run average in 15 innings.
Lohse (14-8) worked 7 1/3 innings, scattering seven hits and one unearned run with five strikeouts, while Halladay (18-6) gave up four runs on six hits in eight full frames.
Meanwhile, in Atlanta on Sunday the Mets helped the Cards' cause, as Ruben Tejada's RBI single in the eighth inning put New York ahead for good in a 7-5 victory over the Braves in the rubber match of a three-game series.
Tejada had two hits and knocked in four runs as the Mets won for the second time in three games.
Byrdak signed a one-year contract with the Mets after the game.