The Rangers were aiming for Darvish to begin his rehab assignment on Tuesday. But Darvish changed his mind after throwing 47 pitches in a live batting practice session on Thursday in Arlington.
"His velocity was up from where it has been," pitching coach Doug Brocail said. "He was strong, he just wasn't happy with his off-speed stuff. He has his fastball, cutter and slider, he's not happy with the changeup and the curveball."
Brocail said the plan is for Darvish to throw 60 pitches in four increments of 15 each. If that goes well, he could start his rehab assignment on May 1 with Double A Frisco.
The Rangers want Darvish to make at least three starts on a medical rehabilitation assignment. The plan would be to throw 45 pitches over three innings on May 1, 60 pitches over four innings on May 6 and 75 pitches over five innings on May 11.
The next step would be 90 pitches over six innings on May 16. But Darvish could do that in the Major Leagues as well as the Minors.
"We're not counting on it," Brocail said. "But if he comes back (after May 11) and says, 'I'm ready to go,' the horse is out of the stall. You've got to let the horse run. It's up to him. It's all how he rebounds."
T.R. Sullivan has covered the Rangers since 1989, and for MLB.com since 2006. Follow him on Twitter @Sullivan_Ranger and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.