The game will be made up on July 14 beginning at 1:20 CT. July 14 was originally a day off for both teams.
Pirates left-hander Dave Williams, originally scheduled to start Saturday, will be pushed back to Monday against Houston at PNC Park.
"I like the way Fogg pitches in this ballpark (Wrigley Field) and Dave Williams has had some success against Houston," Pittsburgh manager Lloyd McClendon said.
"He's OK," Baker said. "I just didn't want to take a chance with the field conditions."