Hardy injured the thumb in the second inning of the Orioles' 10-3 win against the Cardinals on Saturday when he slid into catcher A.J. Pierzynski at home plate. He played the remainder of that game and was scratched about a half-hour before Baltimore's 8-3 loss to St. Louis on Sunday.
Utility infielder Ryan Flaherty filled in for Hardy at shortstop for the second straight game, and Jonathan Schoop started at second base. Hardy was batting .283 with six home runs entering Monday.
Hardy had X-rays on the thumb, and there's not much he can do to treat the injury at the moment. He has been wearing a splint on the hand at times and is now trying to restore its mobility.
"Sometimes the stiffness and soreness comes from being immobile for a while," manager Buck Showalter said.
Hardy said the thumb didn't feel much different on Monday than it did the day before, but he's optimistic that he can avoid a trip to the disabled list.
For now, the O's can use Flaherty as a replacement at shortstop. If the injury shelves Hardy for long, though, then they have other options.
"I hope he [can be used off the bench today]," Showalter said before Monday's series opener against the Yankees at Oriole Park at Camden Yards. "He was going in that game yesterday if we had gone ahead. I can't tell you where we are with that now because I'm not going to broadcast it, but I'm hoping it's short. Something like this, it's day to day."
Brittany Ghiroli is a reporter for MLB.com. Read her blog, Britt's Bird Watch, and follow her on Facebook and Twitter @britt_ghiroli. David Wilson is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.