"He didn't report anything -- he didn't even flinch -- but over the course of the last couple days, it's gotten really sore," manager A.J. Hinch said. "He didn't look right throwing the ball the other day."
Although rosters expand Friday, Houston placed Gattis on the DL to open a roster spot for Juan Centeno, who got the start behind the plate Thursday against the Rangers. Hinch believed it would be at least 10-14 days before Gattis was ready to return.
Yuli Gurriel, who left Wednesday night's game with a sore right knee, was not in the lineup for Thursday's series finale, but Hinch said there are no plans to put him on the DL.
"He's OK; he's day to day," Hinch said. "He's not going to play [Thursday] and we have a day off [Friday]. My hope is that he's going to be able to play at least one of the games on Saturday [in the doubleheader against the Mets]. It's just knee soreness, inflammation that he's got to get out of there. The least amount of activity that he can do, the better."
In other injury news, right-hander Lance McCullers Jr. made his second and presumably final Minor League rehab start Wednesday night, allowing two runs over five innings for Double-A Corpus Christi. McCullers, out since July 31 with a back injury, went on to throw about 15 more pitches in the bullpen, seemingly having no issues.
"His stuff was pretty good," Hinch said. "He was in the low-to-mid 90s, which was a good sign. His breaking ball was a little bit better. He threw quite a few changeups. It was a normal game for him, so I think that's a good sign,"
McCullers will join the Astros in Houston and be re-evaluated on Saturday.
"It's basically the end of the Minor League season, so we need to determine what the next step is for him," Hinch said. "We're hopeful that he's going to start sometime next week."
Hinch wouldn't say who McCullers would replace in the rotation, though with doubleheaders slated for each of the next two Saturdays, the manager noted that the Astros are "going to need as much starting pitching as we can get."
Third baseman Colin Moran, who sustained a facial fracture on July 22 after fouling a ball into his face, will head to Class A Quad Cities to begin a rehab assignment with an eye on returning in September.
Moran, who has been taking at-bats in the Gulf Coast League, is the Astros' No. 7 prospect, according to MLB Pipeline. He was 3-for-6 with a home run in two games with Houston before the injury.
Mark Feinsand is an executive reporter for MLB.com and covered the Astros on Thursday.