CHICAGO -- The Cubs activated Edward Cabrera from the injured list in time for the right-hander to start against the Cardinals on Sunday.
Cabrera, 28, has been out since late June because of a left hamstring strain, which he suffered while covering first base. He is 5-4 with a 5.10 ERA in 14 starts for Chicago this season, his first with the Cubs.
To make room on the roster for Cabrera, the Cubs demoted right-hander Javier Assad to Triple-A Iowa.
"The decision we made is just to preserve every pitcher that we could," Cubs manager Craig Counsell said Sunday morning. "If I'm in Javier's shoes, that doesn't feel fair. But from a depth perspective, this was a way to preserve everybody."
Assad, 29, has pitched well this season but has minor league options. He is 6-1 with a 3.59 ERA in 21 games for the Cubs, including 10 starts.
The return of Cabrera also pushes left-hander David Peterson into a bullpen role for the moment, but Counsell didn't commit to any longer-term plans as the Cubs have competition within their rotation.
"We're at go time here," Counsell said of Cabrera. "We're at a stage with the people on the roster that it's go time. Edward understands that."
The Cubs' rotation is as deep as it has been all season. The trade deadline additions of Clay Holmes and Kevin Gausman have given Chicago options it didn't possess a month ago.
The reinforcements have forced Assad to the minors and Colin Rea, along with Peterson, to the bullpen. The team is still expecting relievers Hoby Milner (appendicitis), Daniel Palencia (forearm) and Ben Brown (neck) back before the end of the season.