"It felt good to be out there. I'm not going to lie," Prior said. "I had some anxiety going and probably a little nervousness going into it."
Chicago lost for the eighth time in 11 games when the Cubs' bullpen blew a 1-0 lead. Jack Wilson doubled off Joe Borowski (2-4) and scored on Craig Wilson's two-out single to tie it. Pinch-hitter Chris Stynes then hit a go-ahead single off Mike Remlinger.
"To come in against Prior that's going to be tough from the first pitch. We definitely needed this win after dropping five in a row," Wilson said.
Salomon Torres (4-1) got the win and Jose Mesa pitched the ninth for his 14th save as the Pirates ended a five-game losing streak.
Phillies 9, Braves 1
In Atlanta, Bobby Abreu and Mike Lieberthal homered to back seven impressive innings by Eric Milton as Philadelphia beat Atlanta to end a four-game losing streak.
Milton (7-1) held the Braves scoreless after the first inning, allowing just one earned run and five hits overall. The left-hander struck out five and walked two.
Pitching opposite Travis Smith (0-2) for the second time in six days, Milton retired 10 straight after Eli Marrero walked with two outs in the first. He also escaped a jam in the fifth with runners on first and second and one out when Nick Green popped up and Julio Franco grounded into a fielder's choice.
Smith, filling in for injured starter Horacio Ramirez, allowed six hits, three earned runs and one walk.
Cardinals 5, Astros 3
In St. Louis, Scott Rolen snapped a fifth-inning tie with a two-run single, giving him a major league-leading 57 RBIs and sending St. Louis past Houston.
The Cardinals have won five in a row and eight of nine to pull within a game of NL Central-leading Cincinnati.
St. Louis won without manager Tony La Russa, serving the first game of a two-game suspension for his shouting match with Pirates manager Lloyd McClendon on Thursday.
Dodgers 7, Diamondbacks 3
In Phoenix, Paul Lo Duca hit a three-run homer and Milton Bradley, playing while appealing a four-game suspension, drove in two runs to help Los Angeles beat Arizona for its fifth win in six games.
Kazuhisa Ishii (7-3) overcame six walks and improved to 5-1 against Arizona. He allowed three runs on four hits.
Guillermo Mota allowed two hits in two innings for the save.
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