Suppan pitched five-hit ball into the sixth inning for his first win since September, leading the Cardinals to an 11-1 victory over the Pittsburgh Pirates.
Albert Pujols hit his 24th homer and finished with three hits as the NL Central-leading Cardinals improved to 11-5 since the All-Star break. They remained a half-game ahead of Cincinnati, which beat Atlanta 5-2.
St. Louis also strengthened its rotation before the game, acquiring Jake Westbrook from Cleveland in a three-team deal. Westbrook is expected to join the team Sunday and start Monday against Houston.
Suppan (1-6) struck out five in 5 1/3 scoreless innings but manager Tony La Russa was noncommittal about the right-hander's future.
"Nobody's guaranteed playing time," La Russa said. "When he first showed he had no guarantees. There was an opportunity. He got his first win but he's given us a chance to win in a whole bunch of games."
Suppan, who earned his first victory since Sept. 19 for Milwaukee, said the decision is out of his control.
"I feel like I'm throwing better now than when I first got here," said Suppan, who signed with St. Louis in June. "I feel good about that. I gave everything I could give."
Colby Rasmus hit a two-run homer and an RBI single for the Cardinals, who used five relievers to finish it out. It Rasmus' career-high 17th homer and first since June 27.
"I did feel pretty comfortable out there," Rasmus said. "I'm not trying to reach for the stars; just play the game like I could play it."
Jeff Clement homered in the eighth for Pittsburgh, which made a handful of trades before the non-waiver deadline during another difficult season. Jose Tabata went 3 for 4 to extend his hitting streak to 11 games.
The Pirates sent left-handed reliever Javier Lopez to San Francisco and closer Octavio Dotel to the Los Angeles Dodgers, gaining a total of six players whose rights they control for several years. They also acquired catcher Chris Snyder from the Arizona Diamondbacks in a five-player swap.
Pirates starter Daniel McCutchen (1-5) issued six walks while yielding four runs, three earned, and six hits in 5 2/3 innings.
"I thought he battled," manager John Russell said. "You could tell he was competing and getting after it. He didn't really have his best stuff. The last inning, we knew was a stretch and we tried to get him through it."
Clement and McCutchen were recalled from Triple-A Indianapolis earlier in the day.
St. Louis scored at least one run in six innings. Suppan hit an RBI single in the second, Rasmus scored on first baseman Garrett Jones' throwing error in the fourth and Pujols connected in the fifth, hitting a 2-0 pitch into the bleachers in right-center to give him 72 RBIs.
Former Cardinals manager and 2010 Hall of Fame inductee Whitey Herzog was honored in a pregame ceremony in which his No. 24 was retired. ... Tabata is batting .373 (25 for 67) since the All-Star break.