DETROIT -- An error made the difference in a game of miscues.
Tied 3-3, Detroit had two men on base with two outs when Monroe popped to left field. Ryan Klesko misjudged the ball and it fell safely, allowing Placido Polanco and Rondell White to score. Polanco led off with a single and White walked.
"I was too aggressive coming in for the ball," Klesko said. "The wind was changing directions throughout the game. ... It cost us the game."
The Tigers made two errors that led to Padres' runs.
Fernando Rodney (1-0) got the win, allowing a run and two hits in an inning of relief.
Jake Peavy (5-2) took the loss, allowing three earned runs and four hits in six innings. He struck out 10 and walked two.
"It's a big win," Tigers manager Alan Trammell said. "Jake Peavy led the National League in ERA last year."
The game was delayed by rain for 1 hour, 43 minutes with one out in the bottom of the second. A sudden downpour lasted only about 15 minutes, but the grounds crew wasn't able to get the tarp on the field before the third-base line and the left side of the infield became a quagmire. It then took the remaining time to repair the damage.
Peavy remained in the game after the delay, but Tigers starter Jason Johnson gave way to Matt Ginter to start the third.
He only allowed an unearned run and three hits in three innings.
"Just try to go in and throw up zeros," said Ginter. "Keep the team in it."
San Diego took a 1-0 lead in the third on an error by first baseman Dmitri Young on Klesko's grounder with two outs, allowing Khalil Greene to score from third.
But Detroit came back with three runs in the bottom of the third.
With two outs, Brandon Inge homered to center field, his sixth of the season, also scoring Nook Logan, who had walked and stolen second. Polanco followed with a double and Young's single to left brought home Polanco.
"That was the only part of the game that I didn't feel I was in complete control," said Peavy. "I just can't stand to lose a ballgame."
San Diego tied it in the sixth. Phil Nevin singled in Klesko, who reached on a two-base error by pitcher Doug Creek, and Mark Sweeney drove in Nevin with a double to right-center. Both RBI hits were against Rodney. Sweeney also homered in the ninth.
The Tigers added three runs in the eighth. White tripled in a run and Ivan Rodriguez and Monroe each had RBI singles.