The Jets rushing attack will have a different look this week.

Running back Braelon Allen is seeking a second opinion on his injured left knee, but coach Aaron Glenn described it as “a pretty serious knee injury.”

A source confirmed the initial diagnosis was a sprained MCL, but Glenn said the Jets want to wait until Allen gets the second opinion before deciding whether to put him on injured reserve, which would mean he would miss at least four games.

“We’ll see exactly where he’s going to be when it comes to designating if he’s going to be on IR or not,” Glenn said.

Allen is the team’s third-leading rusher with 18 rushes for 76 yards and one touchdown, but it appeared he was going to be a big part of the game plan against the Dolphins on Monday night before the injury.

He had four rushes for 29 yards on the first Jets drive, but he fumbled at the goal line and the Dolphins recovered. The injury occurred in the second quarter of Monday’s 27-21 loss when Allen was returning a kickoff and was hit on his knee.

Braelon Allen, being tended to by trainers, exited with a left knee injury in the Jets' Week 3 loss to the Dolphins.Braelon Allen, being tended to by trainers, exited with a left knee injury in the Jets’ Week 3 loss to the Dolphins. Charles Wenzelberg / New York Post

The Jets will have Isaiah Davis serve as Breece Hall’s backup against the Cowboys on Sunday. Davis has been primarily a third-down back. Kene Nwangwu is the other running back on the roster, but he has missed three games with a hamstring injury.

“Isaiah’s a great back,” quarterback Justin Fields said. “We’ve got Kene as well. Like I’ve said since OTAs, since I got here, our running back room is loaded.”

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Glenn said DE Jermaine Johnson (ankle) is “day to day.” He has missed the past two games.

The Jets did not practice Wednesday but estimated that Johnson would not have practiced if they did.

Glenn said Nwangwu is also day to day. CB Michael Carter II (concussion) is not expected to be ready for Sunday, Glenn said.

Jarvis BrownleeJr., who the team acquired in a trade last week, is practicing and could take Carter’s place Sunday. TE Mason Taylor was listed on the injury report with an ankle injury and was estimated as a limited participant in practice.