Sources: NFL, NFLPA reviewing T.J. Watt concussion, protocol

PITTSBURGH -- The NFL and NFL Players Association are jointly reviewing T.J. Watt's concussion and the concussion protocol after the Steelers pass rusher entered the protocol a day after taking a hard hit early in Pittsburgh's Thursday night loss to the New England Patriots, a league source confirmed to ESPN.

Watt entered the league's concussion protocol Friday morning after he arrived at the Steelers' practice facility and reported concussion symptoms following Thursday night's game. Watt was hit in the face by running back Ezekiel Elliott's knee on the first play of the game. He missed just two plays before returning to the field.

The review, which is standard when a player enters the protocol, will involve a review of video and medical report, as well as interviews with Watt, the Steelers' medical staff and independent medical staff.

On Tuesday, Steelers coach Mike Tomlin said he believed Watt was evaluated for a concussion on the sideline, but he was "not aware" Watt re-entered the game wearing a visor with a darker tint.

"I assume that he was," Tomlin said when asked if Watt was checked for a concussion. "But again, I'm managing the game. I leave that to the medical experts. They essentially tell me whether someone is out, whether they're subject to return or whether they're back. I got a report that [Watt] was subject to return and then I got a report that he was back, and that was just my knowledge of the details of what transpired with him during the time that he was out in-game."

Both Watt and fellow starting outside linebacker Alex Highsmith, also in the concussion protocol, were limited participants in Tuesday's practice.

The review was first reported by NFL Network.