SAN FRANCISCO -- D-backs starter Trevor Cahill completed his second throwing session earlier this week, and manager Kirk Gibson said Friday he did not know when the right-hander would throw next.
In the latest outing, Cahill threw 40 pitches after tossing 20 in his first session.
"He threw the ball well, working on some mechanics," Gibson said. "He threw the ball much better than he did the first time."
Gibson added that Cahill is "way behind [Brandon] McCarthy," who is set to begin a rehab assignment with Triple-A Reno on Sunday.
Cahill has been on the disabled list since July 1 with a right hip contusion and was slowed by shoulder soreness two weeks ago, although the shoulder issue has subsided.
Last week, D-backs general manager Kevin Towers said it looked like Cahill might not be able to return until early August.
This has been Cahill's toughest season in his five-year big league career. Before the injury, he was 3-10 with a 4.66 ERA in 17 starts.