"My arm feels better than it did a week ago when I started throwing breaking balls," said Billingsley. "I think throwing harder has helped me get extension and loosened up the flexor muscles."
Billingsley had Tommy John surgery last year on April 25, and he appears to be on track for a May return. He expects to throw several more bullpen sessions before graduating to face live hitters, then game action.
In other Tommy John surgery news, prospect Ross Stripling returned to camp after having an arthroscopic procedure on his right elbow in preparation for Tommy John reconstruction, which will take place after the swelling subsides, probably in two weeks.
Ken Gurnick is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.