Second-round draft pick Marvin Austin and free-agent cornerback Brian Witherspoon also are going to need season-ending surgery, a disappointed coach Tom Coughlin said in going over his injury report in a conference call.
"The injury report is not something that I'm real happy about today," Coughlin said. "I feel very badly for these young guys who have prepared and played so darn well and then had their seasons come to an end."
Thomas, who was in the final year of his contract, tore the ACL in his right knee late in the first half and will need surgery.
Austin tore a pectoral muscle on his left side and will miss his second straight season. He was suspended by North Carolina last year and was ineligible to play.
Witherspoon tore the anterior cruciate ligament in his left knee in the second half of the Giants' 41-13 win. He was placed on waived-injured list.
The Giants' injuries at cornerback are reaching a crisis point. Backup Bruce Johnson was lost early in training camp with an Achilles' tendon. First-round draft pick Prince Amukamara broke a foot days after arriving. And now Thomas and Witherspoon are down.
That leaves Corey Webster as the lone returning starter and former first-round pick Aaron Ross to move into the other starting spot. Mike Coe, first-year pro, Joe Burnett and rookie Darnell Burks are the only other cornerbacks on the roster.
General manager Jerry Reese said after last night's game that the Giants would be looking to sign cornerbacks, and co-owner John Mara said Tuesday that the team would be able to free up cap room to sign a veteran, if a good one could be found.
Ross is not the problem. He was a starter for a couple of seasons before his playing time was limited the past two seasons by hamstring injuries and Thomas' development.
"I think Aaron Ross played well last night and he has had a good camp and now he is a guy that our team will turn to and he realizes that," Coughlin said. "Hopefully, he is just going to get some consistency in his play and I think he will step up and realize that our team is looking to him. We need him for the reason that he was brought here and will go on to help us this year."
Ross welcomed the challenge after the game on Monday night.
"That comes with the territory," he said. "A teammate went down. Now it's my job to fill in. I am ready to get back on the field. Hopefully, the coaches have confidence in me. I've been ready from day 1. I will take the challenge on."
Coughlin was not sure when Amukamara will return. He has been getting around the team headquarters with the aid of a razor scooter.
"From the information I'm getting, he's still a 10-week kind of rehab and recovery," Coughlin said. "As you've seen, he's still in a boot."
Reese said the rookie from Nebraska is going to have to make do without the benefit of a training camp.
"He's got first-round talent," Reese said. "We're not going to rush him back because we don't want him to have a setback. So hopefully, we'll get him out after Week 4 and get him acclimated to the speed of the game and he can jump in quickly to help us out."
The Giants did get a little help on Tuesday, signing veteran defensive tackle Jimmy Kennedy, a nine-year veteran who has played with the Rams, Broncos, Bears, Jaguars and Vikings. He has played in 86 regular-season games with 31 starts and in five postseason games with two starts. His career totals include 188 tackles, 8.5 sacks, five passes defensed, two forced fumbles and two fumble recoveries in the regular season and 10 tackles and 2.0 sacks in the postseason. He had a career-high 55 tackles in 2006 and a career-best 3.0 sacks in both 2005 and 2009.
Copyright 2011 by The Associated Press