"He kind of aggravated, strained the groin on his last at-bat running down the line to first," Porter said. "With it being a day game after a night game, I just told him we're going to give you [Thursday], and then Friday, you'll be right back in there."
Altuve's 2-for-5 night on Wednesday broke his streak of eight straight games without multiple hits.
Porter said Altuve could have played Thursday, but he didn't want to chance it with the Astros in the midst of 20 straight games without an off-day.
"He could have gone, but I lean on the side of caution," Porter said. "Jose plays the game all out, and he's on the basepaths a lot. I didn't want him hesitant, and I didn't want him aggravating it more with us getting on a flight right after the game."
Houston goes on the road for six games after the Orioles series. Regular shortstop Marwin Gonzalez started at second in place of Altuve, and Ronny Cedeno started at shortstop.
Chris Abshire is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.