Jacquian Williams

This is believed to be the second-quarter play where Giants linebacker Jacquian Williams suffered a concussion.

((AP Photo/Scott Eklund))

EAST RUTHERFORD ‐ The play occurred early in the second quarter. Giants linebacker Jacquian Williams tackled Seattle Seahawks running back Robert Turbin low before fellow linebacker Jameel McClain came in high and forced a fumble. Safety Antrel Rolle recovered.

Williams celebrated momentarily and walked off the field. The Giants believe that was the play on which he suffered a concussion that has kept him out of practice this week.

Williams played every defensive snap of the game for the Giants, presumably most of the final three quarters with a concussion. He finished with a season-worst -5.3 grade, according to Pro Football Focus.

"I would attribute [the injury] to that [play]," defensive coordinator Perry Fewell said on Thursday. "When we looked at it on film, I think it was when Antrel Rolle recovered the fumble. I think at about the 49-yard line.

"That's when we assumed he got hit. There was nothing any different talking to him, communicating with him, talking to him on the sidelines, so no, we couldn’t tell anything during the ball game."

A Giants spokesman said Williams did not develop any symptoms or say anything about the injury until the team returned home from Seattle. The spokesman said Williams told the team he was experiencing headaches on Monday. Several teammates also said they didn't notice any difference with Williams in the huddle.

Williams and running back Peyton Hillis, both dealing with concussions, were sent home from the Giants facility on Wednesday. When asked how they were doing, coach Tom Coughlin said "not good" and that they were under doctor supervision.

Williams was on the sideline in street clothes during the early portion of practice on Thursday.

Concussions have been a hot topic in recent years. The league has altered its concussion protocol in regards to the in-game handling of them and post-concussion management.

According to an NFL.com report in October 2013:

Given the recent findings of CTE in deceased NFL players, the league, teams and players have proceeded with extra caution in recent years. But clearly the protocol for recognizing concussions is not perfect. There still isn't a foolproof way of diagnosing all concussions on the spot during a game.

The result is players like Williams play almost three full quarters with a brain injury.

Jordan Raanan may be reached at jraanan@njadvancemedia.com. Follow him on Twitter @JordanRaanan. Find NJ.com Giants on Facebook.