The A's are targeting the end of April, or the beginning of May, for Gray's return to the rotation. By that point, he should be built up to at least 90 pitches, just as he typically would when exiting Spring Training healthy.
Gray, who received his diagnosis a month ago, threw three bullpen sessions before facing hitters for the first time in Kansas City on Thursday afternoon.
"I think if you look back at the way the throwing has gone ... to be able to do all that and still feel healthy and still feel strong and everything feel good, that's quite a bit of volume you're putting on your body and your arm, and to be able to recover and bounce back, it's a really good sign," Gray said. "I felt good today. It's always different when you get hitters in there. Now, I'm looking forward to the next step."
Gray warmed up with 30 pitches in the bullpen at Kauffman Stadium, before throwing two sets of 15 pitches to hitters.
"It went really well," manager Bob Melvin said. "When he's on, he's got that late movement, and it can cut, it can sink. He had that today. He had a good breaking ball. Like he normally is, he was really intense in what he was doing out there. I know he felt good about it."
A's starters entered Thursday with a combined 3.99 ERA. Three times, in the first five games of this six-game road trip, a rotation member had allowed one run or fewer.
"It's great to see," Gray said. "Everyone knew that there was a ton of talent and guys that really want to go out there and compete, and that's just what they've done. It's been awesome to watch, and I'm really glad I got to come on the road trip to see it and to be around, because I have every intention of being a big part of this when I get back.
"So to be around and to be with the starters and the rest of the guys, I'm glad I got to do that. It really pushes you and makes you want to get back in it and do your part to contribute. They've been awesome."
Jane Lee has covered the A's for MLB.com since 2010.