In the darkness of the film room, Rey Maualuga saw the light.

The Cincinnati Bengals linebacker had struggled since returning from a knee injury that kept him out most of the preseason. Playing at a career-high 267 pounds, Maualuga was slow, sluggish and, during a warm September game in Washington in Week 3, gassed.

The day after the Redskins game, Bengals linebackers coach Paul Guenther called Maualuga in for some vintage film study.

“I went back and looked at his rookie tape, and he was a lot lighter,” Guenther said. “And his movement, it looked like a different person. I said, ‘Rey, this is a different guy on this tape. You’ve got to lose weight.’ I put on back-to-back plays of him now and him then, and he saw it.”

In less than two months, Maualuga has shed 20 pounds.

“It’s taking care of your body, eat the right things and not snack on chips or frozen foods,” Maualuga said. “I watch my diet and keep it consistent.”

In addition to watching what he eats, Maualuga has been doing extra running while wearing a sweatshirt. And as the weight fell off, his play picked up. Sunday against the New York Giants, Maualuga had a season-high 11 solo tackles as part of his team-high 13 stops.

“I think it was his best game since he’s been here,” Guenther said. “Overall he made very little errors, made good plays and covered well. The whole thing.”

Maualuga said the reason he initially added the weight was because he thought it would help him against the run. But all it did was slow him down and tire him out to the point where he was becoming a liability. Not only was he struggling to shed blocks and make tackles, he was having a hard time catching his breath and communicating in the huddle.

“There were times on long drives when he couldn’t even make the call earlier in the season,” Guenther said. “I think that was 90 percent why he wasn’t doing things the way we wanted him to, was fatigue. You can’t worry about if you’re winded. You’ve got to get up off the ground, call the huddle, call the adjustments and play good. Now he’s doing it.”

With Maualuga moving quicker, Guenther has been able to move him further back from the line of scrimmage. That’s giving Maualuga a better view of the play as it develops, so he’s recognizing things quicker in addition to moving faster.

“It’s a different league,” Maualuga said. “It’s not smashmouth. There’s no need to be that big anymore. I’m still physical enough to be able to come down and hit someone.”

Maualuga’s new frame and improved conditioning will be tested Sunday when the Bengals travel to Kansas City to face Jamaal Charles and the NFL’s No. 4-ranked rushing offense.

“They’ve got an awesome running game,” Maualuga said. “Jamaal Charles is very fast and slick out of the backfield. We can’t have him running full speed through the holes and to the outside of the perimeter”

The Chiefs also have power options in Peyton Hills and Shaun Draughn.

“Their offensive line is very good, and I kind of see out of them what Houston ran based on their line coming off the ball and blocking,” Maualuga said. “We’ve got a lot to prepare for. It’s going to be a physical game.”

The Bengals rush defense ranks 20th in the league, but that is slowly improving thanks to a sleeker Maualuga patrolling the middle of the field.

“You have to be coach-able, accept certain things and drop some weight,” he said. “That’s what I did. Coach Guenther will joke around and ask who the heaviest linebacker in the room. Now there isn’t that huge gap anymore.”