Peavy allowed four runs before leaving after one inning, the shortest outing of his career, due to a viral upper respiratory infection.
The Phillies kept piling it on after Peavy was gone. Ibanez hit his 200th and 201st career homers - both two-run shots - and Greg Dobbs also connected for Philadelphia, which won its fifth straight game.
San Diego's Adrian Gonzalez hit his major league-leading 22nd homer.
The Phillies made Bastardo's night a little easier by handing him a 4-0 lead before he took the mound. The 23-year-old from the Dominican Republic held the Padres to one run and four hits in six innings, struck out five and walked one.
Bastardo (1-0) was selected from Triple-A Lehigh Valley and takes Brett Myers' spot in the rotation. Myers will have hip surgery on Thursday that likely will end his season.
Ryan Madson came on with the bases loaded and two outs in the ninth and got Kevin Kouzmanoff to hit into a force, earning his second save in as many chances.
Peavy (5-6), the 2007 NL Cy Young Award winner, allowed three hits, two walks and a sacrifice fly. He walked Shane Victorino and Chase Utley with one out before Ryan Howard doubled them in. Ibanez doubled in Howard, then scored on Dobbs' sacrifice fly.
Peavy's previous shortest start was two innings at Arizona on Aug. 25, 2003, during his first full big league season.
Ibanez homered to center off Josh Geer with no outs in the third to make it 6-0, and then to right off Joe Thatcher with one out in the seventh to make it 10-1. Howard was aboard on a walk for Ibanez's first homer and Chase Utley was aboard on a walk for his second.
Ibanez came up with the bases loaded and one out in the eighth but hit into a double play. He finished with three hits and three runs.
Dobbs homered to right off Luis Perdomo with two outs in the fifth, his second.
Gonzalez homered into the home-run porch in the right-field corner on a 1-0 pitch with one out in the sixth. He also drew a bases-loaded walk in the four-run seventh. His older brother, Edgar, hit an RBI single and Chase Headley had a two-run base hit.
Notes:@ Phillies reliever J.C. Romero is due to return on Wednesday from a 50-game suspension for testing positive for a banned substance. He's been pitching in the minor leagues. "We'll run him out there," manager Charlie Manuel said. "We'll put him on lefties. Who knows, we might put him on righties too, early. It depends. He'll pitch and he'll eventually work his way right back to where he was at." ... Neither team took batting practice because of a California League game between Lake Elsinore, San Diego's Single-A affiliate, and Rancho Cucamonga. Lake Elsinore won 6-2.
Copyright 2009 The Associated Press.