"He's throwing hard down there," Melvin said. "Sometimes it's tough to look like you're throwing 100 percent, and it does with him. The intensity is there with him. He's looking forward to throwing to hitters and, more than anything, looking forward to getting out on a rehab and throwing in games."
Gray could get game action on a Minor League rehab stint after Thursday's session. The A's expect him back in their rotation by the end of the month.
Right-hander Chris Bassitt, meanwhile, is still eyeing a June return. The rehabbing pitcher, who underwent Tommy John surgery last year, threw to hitters in Stockton, Calif., on Sunday. He totaled 30 pitches, 15 each in a pair of simulated innings.
"He threw all of his pitches and felt great," Melvin said.
Jane Lee has covered the A's for MLB.com since 2010. Follow her on Twitter @JaneMLB. This story was not subject to the approval of Major League Baseball or its clubs.