Carlos Zambrano is out two or three weeks after being placed on the disabled list due to a strained left hamstring.
The right-hander was injured while running out a bunt for a hit in Sunday's win over the Florida Marlins on Sunday. Zambrano pitched five innings and earned the victory before leaving. He is 3-1 with a 4.50 ERA on the season.
Piniella said the Cubs plan to call up right-hander Randy Wells from Triple-A Iowa on Friday to take Zambrano's spot in the rotation at Milwaukee. Wells is 3-0 with a 3.13 ERA. He will be making his first major league start. He made four appearances as a reliever for the Cubs in 2008.