It's the third time in less than two years that Coles is dealing with a head injury. He had his streak of playing in 107 straight games end last November because of a concussion and was briefly knocked unconscious when he was leveled by a hit by Miami's Zach Thomas in December 2006.
Coles didn't practice Wednesday, when he was listed on the team's injury report as having "head" and "thigh" ailments. He participated in warmups Thursday during the 30-minute window the media are allowed to watch but didn't participate in 11-on-11 drills for the second straight day.
"Yeah, it's a concussion," coach Eric Mangini acknowledged Thursday. "I just listed it that way because I list all the body parts. Yeah, that's a concussion."
Mangini also confirmed that safety Eric Smith suffered his second concussion in three weeks, and his status is also unclear. He was limited in practice for the second day in a row.
Coles, also nursing a strained thigh since training camp, was hit hard after trying to catch a pass late in the second half of New York's 16-13 overtime loss at Oakland. Coles came up with a facemask full of grass and appeared a bit dazed but was able to return despite the injury.
"Those aren't coaching decisions," Mangini said. "We won't put anybody back in the game until they're cleared medically to go back in the game."
Coles, who leads the Jets with 30 catches for 369 yards and four touchdowns, refused to address the injury, citing the team's policy of not discussing them publicly.
"Y'all know we're not allowed to talk anything about that type of stuff, so why would you even put me in that position?" he said. "Understand that if I speak anything about any type of injury, that it's considered conduct detrimental to the team.
"Unless any of y'all are going to fork over some cash, don't ask me no more damn questions about it. Talk to Eric and talk to the doctors," he said.
Smith was initially injured when he collided with Arizona's Anquan Boldin on a helmet-to-helmet hit on Sept. 28 that drew the safety a one-game suspension and $50,000 fine. Mangini was uncertain when the latest injury occurred.
"I can't remember if it was on a special teams play that he was in or one of the sideline tackles," Mangini said. "But once it happened, again, he goes to the doctors, the trainers and at that point, it becomes a medical decision, not a coaching decision."
Unlike Coles, Smith did not return to the game after the injury but participated in special teams drills early in practice.
Tight end Bubba Franks (hip) and right tackle Damien Woody (calf) did not practice Thursday, while wide receiver Jerricho Cotchery (shoulder), tight end Chris Baker (back) and right guard Brandon Moore (foot) were limited.