"I am still the same size and the same speed but a lot more angrier," said the star linebacker.
Merriman, a Pro Bowler in his defensive rookie of the year season, has served his four-game suspension for steroids. When leaving the Chargers, he was their leading sacker with 8.5 -- a number which is currently just one shy of Shaun Phillips' team-best 9.5.
So what happens when Merriman returns to the mix?
"Lights is coming back and teams better watch out," warned defensive tackle Jacques Cesaire, referring to Merriman by his "Lights Out" moniker. "He circled us up the day before he was leaving and he probably won't admit, but I thought he was getting a little teary eyed, misting up a little bit, and he said, 'you hold it down,' and he swore to us he was going to come back with a vengeance.
"I know he is going to come back hard and be like something that people have never seen before."
The Chargers, despite their recent run of success, can use him. With Merriman playing on the left side, that makes Phillips able to do more as teams have to assign two players to Merriman.
"He's a premier outside linebacker in the 3-4 scheme and a real good down rusher in the four man scheme," Bills head coach Dick Jauron. "He brings that back to them, but they're good enough without it. In his absence, they're 4-0, so it's tough and it's tough to game plan for him because they get that mismatch of him on a fullback or halfback and he takes advantage of it.
Merriman's presence also will help the back end, which has been exposed of late. With a feisty Merriman pestering quarterbacks, the defensive backs won't have to cover for as long.
The Chargers will also be looking for a bounce-back game from Philip Rivers. The first-year starter has been a sensation this season, ranking among the league-leaders in nearly every critical category.
But against the Raiders, Rivers completed but 14-of-31 passes for 133 yards and an interception. He had a career-low 44.2 rating.
"Everyone is accustomed to us coming out and throw the ball up and down the field," coach Marty Schottenheimer said. "That isn't the NFL."
To Rivers' credit, he didn't let his individual woes leak over to his teammates. He said the biggest contribution he had Sunday won't appear on the statistical sheet.
"The best thing I did out there was lead and kept the guys together and kept playing," Rivers said.
What the Chargers have to overcome are sluggish starts. Sure, the come-from-behind wins the last three weeks have been thrilling. But living on the edge often catches up with a team at some point.
"We came out flat," Phillips said. "I don't understand why. That's what we have to learn to do, which is come out from the opening snap on and play all four quarters."
The Chargers are a different team in the final two quarters, where they have outscored rivals, 214-89.
Running back LaDainian Tomlinson said being away from Qualcomm Stadium makes fast starts difficult.
"Just being on the road it's hard to start fast when that's their main objective as a tea, at home to start fast," said Tomlinson, the NFL touchdown leader with 24.
The Chargers have been keen on the road, earning a 4-2 mark. But they know a cross-country trip into chilly Buffalo -- with the Bills coming off an impressive victory over the Jaguars -- will be a test.
"Every week is going to be a challenge and we get one guy back who might help us next week," CB Drayton Florence said of Merrriman. "It's going to be a long trip for us and it is going to be cold weather."