The club discovered that Brandon Laird came down with an illness, suffering from flu-like symptoms, pushing Matt Downs into the starting spot at the hot corner.
Matt Dominguez, who is nursing his wrist injury, still isn't ready to go. Astros manager Tony DeFrancesco said Dominguez may be available late in the game if he got through batting practice without any issues.
Backup Scott Moore, who strained his left groin in Wednesday's loss to the Pirates, is "a few days away," and Laird's sickness makes a trifecta of problems for the Houston infield.
The Astros are going to keep an eye on Laird as he recovers from the sickness, and are taking precautions to ensure he doesn't spread the illness throughout the clubhouse.
"Laird was definitely in the lounge down there sleeping and resting," DeFrancesco said. "Away from everybody."
Downs has played in 16 games at third base this season, and Astros manager Tony DeFrancesco said the club is confident in his abilities.
"We found out we've got a few injuries at third base today," DeFrancesco said. "We've got Downs today, so we're OK. Downs is a good infielder. The ballpark, I heard, is hitter-friendly, and hopefully we get some in those power alleys and get a few homers."
Downs is hitting .204 with seven homers and 14 RBIs in 162 at-bats this season.