Bedard has been awful in dropping his last three outings away from home heading into Tuesday night's matchup with the Phillies, who made him a tough-luck loser on opening day.
Pittsburgh (38-34) activated Jeff Karstens before Monday's contest for his first start in two months, but that backfired when the right-hander gave up seven runs over five innings in an 8-3 defeat.
Bedard (4-7, 4.13 ERA) is next in line after going 0-3 with an 11.08 ERA in his last three road starts, failing to get through the fourth inning in his previous two.
The left-hander turned in a better performance Wednesday as he yielded one run over six innings and did not get a decision in a 2-1 home loss to Minnesota.
Philadelphia (35-40) is 8-16 against left-handed starters, but one of those wins came April 5 at PNC Park when Bedard gave up one run over seven innings in a 1-0 loss as he was outdueled by Roy Halladay. Bedard fell to 2-1 with as 1.61 ERA in four starts against the Phillies.
This is his first outing at Citizens Bank Park since July 3, 2004, when he allowed four runs over seven innings for Baltimore.
Philadelphia jumped on Karstens for four runs in a first inning in which Pittsburgh committed three errors.
"We were aggressive, they started throwing the ball around, starting making mistakes and that helped us get four runs," manager Charlie Manuel said.
Carlos Ruiz had three hits, scored three runs and stole a base as he increased his average to .354. The catcher may be getting even more playing time now that backup Brian Schneider was placed on the 15-day disabled list Monday with a sprained right ankle.
Pittsburgh matched a season high by finishing with four errors. Right fielder Jose Tabata had two on one play in the fateful first inning.
"It happens," manager Clint Hurdle said. "Everybody plays that way some time."
The Pirates have dropped back-to-back games after winning six of seven. Andrew McCutchen is 1 for 8 in these last two defeats after going 15 for 28 with eight RBIs over his previous seven games.
Catcher Rod Barajas left Monday's game with a bone bruise in his left knee. He will be re-evaluated Tuesday.
The Phillies have lost the last four games started by Vance Worley (3-4, 2.78), who is 0-2 with a 2.25 ERA in that span. He has received a total of seven runs of support in that span, yielding two runs over seven innings Thursday in a 4-1 loss to Colorado.
The right-hander, who has no record and a 3.75 ERA in two career starts against the Pirates, has a 3.90 ERA at home compared to his 1.89 mark on the road.
McCutchen has two doubles in five at-bats against Worley.
Copyright 2012 by The Associated Press
This story is from ESPN.com's automated news wire. Wire index
MORE MLB HEADLINES
- Giants win on Pagan's inside-the-park HR
- Yankees rally, win on Overbay's HR in 11th
- Brewers closer Henderson out for hamstring
- Ump regrets botched double-play call on M's