Mangold, who suffered a high-ankle sprain two weeks ago, was declared inactive for Sunday night's 34-17 loss against the Baltimore Ravens at M&T Bank Stadium.
Mangold, who had his streak of 82 consecutive starts snapped last week, worked out for the team's medical staff about two hours before kickoff, but he apparently failed to convince the Jets' brass he was ready. His straight-ahead movement appeared fine, but he seemed a little tentative with his lateral moves.
On Friday, Mangold returned to practice for the first time, but he took only a few reps in team drills. Jets coach Rex Ryan said Mangold was showing improvement, but he didn't sound optimistic. They gave him until Sunday, but with the New England Patriots looming next week -- the Jets' first divisional game -- they decided not to take any chances.
Rookie Colin Baxter made his second NFL start, facing a tough Baltimore front that features defensive tackle Haloti Ngata. The rookie, however, was taken out after quarterback Mark Sanchez fumbled a shotgun snap that was recovered by Baltimore in the second quarter.
"I rocketed it back there," Baxter said. "It was in the vicinity, but it was hot."
In order to mitigate the damage, the Jets moved Matt Slauson to center and inserted Vlad Ducasse at left guard. But Ducasse fared even worse -- standing nearly still on one Baltimore blitz as Ravens defenders shot through the gaps. Baxter was back in at center by the start of the third quarter.
The Jets offensive line was bad yet again, allowing a quarterback who had a broken nose, a badly bruised elbow on his throwing arm and underwent cognitive tests for a possible concussion to be repeatedly knocked to the ground again.
"I think things have to start more up front," said wide receiver Santonio Holmes, one of the few to explicitly target the line. "We have to get a better job from our guys up front. They're focused on it, and that's going to be a big key. Getting Mangold back, he has been a big part that has been missing."
Wayne Hunter is still struggling as the new starter at right tackle as the Jets expedited the process of getting the new center up to speed. Baxter fared well in the remainder of the Jacksonville game after Mangold went down, but he struggled in the loss to Oakland last week as well, and his discomfort was evident after the loss to the Ravens.
"There's the communication issue and then, another snap," Baxter said.
New York's other inactives Sunday night were: Quarterback Kevin O'Connell, wide receiver Logan Payne, safety Emanuel Cook, running back Bilal Powell, tight end Josh Baker and defensive tackle Kenrick Ellis.
Carr has a thigh injury and Smith is nursing a high-ankle sprain. The Ravens were also without safety Haruki Nakamura, who hurt his knee in last week's game against St. Louis. Also on Baltimore's inactive list: Injured wide receivers Lee Evans and David Reed; guard Ben Grubbs; and linebacker Dannell Ellerbe.
Rich Cimini covers the Jets for ESPNNewYork.com. Information from ESPNNewYork.com's Jane McManus and The Associated Press was used in this report.