PHOENIX -- Proof of improvement in Clayton Kershaw was visible Saturday, when the disabled Dodgers ace threw off the bullpen mound for the first time since being injured.

Kershaw, disabled with a strained teres major muscle in his back after winning his Opening Night start in Australia, was not throwing full speed, but wasn't lobbing either.

Manager Don Mattingly said Kershaw remains under orders to hold back on velocity and is monitored by trainers using an app that calculates pitch speed.

"They only allow him to throw so hard," said Mattingly. "Stan [Conte, trainer] has been educating me about the velocity injury. He has to keep it below that so he won't injure it."

No timetable has been placed on Kershaw's return. He has been tossing nearly daily since suffering the injury to retain as much arm strength as possible, but he will require a rehab assignment once he is game-ready.

The teres major muscle, which stabilizes the upper arm to the upper back near the armpit, is a key muscle for acceleration of the arm and resulting pitch velocity.