The right-hander is on the disabled list with a strained left lat, which he first felt during a live batting-practice session on Feb. 17 in Mesa, Ariz. He had not thrown off a mound from that date until Thursday when he threw 25 pitches in Mesa.
"The first throw was kind of like 'ah' and after that it was, 'Let's go,'" Garza said of Thursday's outing. "I felt strong and I felt good. About 18 of the 25 [pitches] were strikes. [It's progressing] slowly, but I'm coming back. Another [bullpen] on Sunday. I can't wait."
Garza feels the arm strength is there, and that he needs to work on his mechanics. Garza will stay with the Cubs while he continues his rehab.
"It made sense to stay there in 90-degree heat [in Arizona] than go to Pittsburgh and try to play catch in 30-degree weather," Garza said. "It was more logic than anything. Now, I'm fine. I want to get off the bump with these guys and just go."
Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter @CarrieMuskat. This story was not subject to the approval of Major League Baseball or its clubs.