"It doesn't really mean anything in terms of setting a timeline or a date, or what it means toward the end of the season," manager A.J. Hinch said. "But to see him get off the mound and look like a pitcher again was definitely the highlight of the day so far."
McCullers will have another bullpen session in a few days, and his response to that will help determine his availability going forward, but Thursday's session, which both Hinch and McCullers said was pain-free, is the first big step in a potential return for the young strikeout machine.
"I think, mentally, I kind of got over the hurdle a week or two ago," McCullers said. "Throwing in general was more of the mental hurdle. … Getting on the mound felt normal, which is good, and my throwing's been really good the last week or two, so I think that's what was able to get [me] up on the hill."
Before his injury, McCullers was emerging into an ace for the Astros in his second season, notching 106 strikeouts and a 3.22 ERA in 14 starts.
"I think not forcing something on [the injury] and letting the rehab and my body respond the way it should and playing off that has been important," McCullers said. "So we're going to continue to do that."
As for Alex Bregman, he's currently undergoing rehab for a hamstring injury suffered during an 8-4 win over the Rangers on Sept. 15, which is expected to sideline him the remainder of the season.
"When you're not out there, it's brutal," Bregman said. "I pretty much lost my voice yelling at the TV this week. I've just been following from afar and trying to get healthy and figure out a way to get back as soon as I can."
Bregman, who was batting .260 with eight home runs and 32 RBIs in his rookie campaign, appeared in good spirits Thursday. The 22-year-old infielder said his rehab process includes some light running and exercise, icing the leg and receiving laser treatment.
While Bregman said he hopes to return to baseball activities soon, the Astros told him to focus less on the timeline and more on the day-to-day process of working through the process.
"He's anxious to test his hamstring," Hinch said. "He doesn't want to believe in the protocol and timeline with these injuries, but he's always in good spirits. … We'll keep testing him and giving him the rehab he needs to get back, whenever that is."
Jordan Ray is a reporter for MLB.com based in Houston.