O'Hara missed practice for the second straight day on Thursday with "swelling and pain" in his left foot and Achilles and may be forced to sit out Sunday's game in Washington.
If O'Hara can't play, left guard Rich Seubert will likely play center. Left tackle David Diehl said on Thursday that that he's been practicing at left guard this week. If Diehl shifts to guard against Washington, Shawn Andrews will likely line up at left tackle, giving the Giants their seventh different starting combination on the offensive line.
O'Hara, however, is holding out hope that he can practice Friday and suit up on Sunday.
"I'm hoping that it feels better by tomorrow. Today was a frustrating day to be [a spectator]," he said.
O'Hara has been hampered throughout the season by a left ankle injury he suffered in training camp, one of several ailments he's dealt with in 2010. O'Hara also injured his left Achilles in the preseason and suffered a mild right Lisfranc sprain in Week 7 at Dallas.
He said there's a "good chance" that he will need surgery during the offseason.
"I think that's something that we're probably going to look at whenever the season ends in February," O'Hara said. "We'll have that option and we'll see what we're going to do but I think there's probably a pretty good chance that I'll need a clean-out of some sort."
O'Hara said the injury flared up midway through the first quarter on Sunday in Green Bay. The ankle was "really sore" after the game and the center took the last two days off to try to limit the swelling.
"It's been tough. I don't feel like I've been able to move like I normally have," said O'Hara, who was voted to the Pro Bowl on Tuesday despite playing in just six games this season. "But that's football and you have to find a way to get the job done."
The ankle and Achilles injuries forced O'Hara to miss three games earlier in the season. He returned for two games against Detroit and Dallas but sat out the next six with the right Lisfranc injury. O'Hara returned to his customary center position against Philadelphia in Week 14.
"I was hoping for the best, hoping that it wouldn't come back and flare up but it did and so I'm just trying to battle," O'Hara said.
Ian Begley is a regular contributor to ESPNNewYork.com.