Hinch said Diaz was experiencing dizziness and was light-headed on the team's bus on the way to RingCentral Coliseum in Oakland on Saturday morning. He was sent to the hospital and was kept overnight to undergo testing and is "fine," Hinch said.
The Astros are "taking every precaution imaginal to make sure he's OK," Hinch said, adding that Diaz should travel back to Houston with the team after their game against the Oakland Athletics on Sunday.
The Astros activated right-hander Brad Peacock (shoulder) from the injured list and recalled right-hander Cy Sneed from Triple-A Round Rock in corresponding moves. The team had an open roster spot after optioning right-hander Rogelio Armenteros to the minors after Saturday's game.
The 29-year-old Diaz, who has started games at first base, second base, shortstop, third base and left field this season, is hitting .267 with seven home runs and 28 RBIs in 45 games.