Pittsburgh Steelers linebacker T.J. Watt (90) warms up before the game against the New England Patriots at Acrisure Stadium. Charles LeClaire-USA TODAY Sports

T.J. Watt left the Steelers Week 14 game after taking a knee to the head from Patriots running back Ezekiel Elliott. Watt returned to action but reported concussion-like symptoms after the contest. The Steelers later placed their top defender in concussion protocol.

Watt was briefly checked for a concussion before being cleared to return on the same drive. The Steelers’ medical staff also took an extended look at Watt’s jaw/mouth, and Watt was spotted wearing a tinted visor later in the game. The NFL and NFLPA have since launched a joint investigation into the Steelers’ handling of this injury, NFL.com’s Ian Rapoport reports.

Mike Tomlin said Monday he was unaware Watt had switched to a tinted visor upon returning to action. The switch certainly looks to be a red flag, with an investigation underway.

“I assume that he was, but again, I’m managing the game,” Tomlin said (via Pro Football Talk’s Mike Florio) when asked if he knew Watt was evaluated for a concussion during 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 he 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 the game.”

The investigation will involve interviews with Watt and both team-affiliated and independent medical personnel involved, according to CBS Sports’ Jonathan Jones. Both Watt and Alex Highsmith, who did not return to action after exiting Thursday’s game early, are in concussion protocol.

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