In just his second practice as a Giant, Amukamara, the team's first-round pick in the 2011 draft, fractured the fifth metatarsal bone in his left foot and will need to have surgery.
Amukamara said he has not been told when he will get the surgery, which will require a screw be inserted into his left foot, but "the sooner, the better." At this point, no timetable on his return has been set and he remains out indefinitely.
"I'm shocked," coach Tom Coughlin said Sunday. "He had some issues working out, but didn't communicate that with us. He said he was sore in that area, too. Who knows?
"We've gone through this before. You wait and wait and wait to get a guy in here, and we were very conscious of the fact that he hadn't been here, so regardless of how he progressed, we were going to take care of him. He wouldn't have taken many snaps. We're disappointed. The only thing we can say now is hopefully he's on track to have a chance to recover."
Amukamara said he suffered the injury while up in press coverage against wide receiver Duke Calhoun in a drill during Saturday night's practice. Both players made a cut, and Amukamara thinks Calhoun may have stepped on his foot during the play.
"I can't put pressure on it right now," said Amukamara, who was using crutches. "I could hobble a little bit, but the team doesn't want me to."
Amukamara went out for the next play, but took himself out of practice shortly thereafter and was escorted off the field by a member from the team's medical staff. X-rays later revealed the fracture.
"I've never broken a bone in my body and I've never had surgery before," said Amukamara, who was selected 19th overall by the Giants out of Nebraska. "It's adversity I'm gonna have to deal with.
"I'm down on myself. I feel like I let my team down and I let myself down. But I can't worry about that, I just need to continue to move forward and persevere."
Amukamara wound up missing the team's first five practices while his agent worked out the details of a four-year, $8.1 million deal, with the first three years fully guaranteed and a little more than half of the fourth year guaranteed. He had his first practice with the team on Friday night after being the last first-rounder in the NFL to sign.
The Giants had hoped that Amukamara would provide them with depth at the cornerback position behind starters Corey Webster and Terrell Thomas, and reserve Aaron Ross. The Giants are now extremely thin at cornerback, having already lost reserve Bruce Johnson, who was waived after he ruptured his Achilles tendon Thursday.
Left tackle William Beatty broke the fifth metatarsal in his right foot last season in the regular-season opener against the Carolina Panthers. He missed two months (six games), but did not go on the injured reserve list.
"Beatty missed (eight weeks)," Coughlin said. "So hopefully it'll be the same (for Prince)."
Mike Mazzeo is a frequent contributor to ESPNNewYork.com.