Signed in March as Bulluck's replacement, Witherspoon easily has replaced the veteran who was allowed to leave in free agency. He's also helped Tennessee (2-1) thrive despite a depleted linebacking corps.
Witherspoon has opened up the season with a sack in each of his first three games tying him for fifth among all linebackers in the NFL in that stat.
Titans coach Jeff Fisher notices not only the sack numbers but the 16 tackles and a forced fumble.
"When he's given a chance to make a play, he makes it. He has a very good understanding of our defense despite being here for just a short time, he's taken over a leadership role there and played through a very, very difficult time in the opener and has settled in and been productive for us," Fisher said.
Witherspoon's debut with Tennessee couldn't have come at a tougher time personally.
His mother, Nora Lee Cooper Witherspoon, died unexpectedly six days before the Titans' season opener against Oakland. He helped bury her, then flew back to Nashville on team owner Bud Adams' plane the night before the opener. Witherspoon got the call to blitz in the first quarter and sacked Jason Campbell.
His performance that day earned him a game ball from his new teammates.
Middle linebacker Stephen Tulloch called Witherspoon's effect on the defense huge.
"Will's a vet, a nine-year veteran. Whenever you lose a guy like Keith, you can't replace him but you can have someone step up, and Will has definitely stepped up to the challenge ... Three straight sacks, it creates momentum swings, and we build off of that and it's a positive so far," Tulloch said.
Witherspoon, who turned 30 in August, was looking for a team where he could be comfortable when he signed his three-year, $11 million contract in March a week after being unexpectedly released by Philadelphia to avoid paying him $5 million for 2010.
He started his career in Carolina in 2002 before signing with St. Louis in 2006. The Rams traded him to Philadelphia last season when he wound up playing in 17 games. He went to college at Georgia, maintains a farm in Missouri and has family in Tennessee.
"It's just an opportunity to be in a place where I feel like I'm at home," Witherspoon said.
The Titans' defensive scheme doesn't hurt either. The Titans host Denver (1-2) on Sunday.
"I just enjoy this team's defensive style ... to come play hard, want to compete and want to be on the field. The defensive scheme is similar to something I've run in the past so there's always a level of comfort," he said.
Witherspoon has been a valuable addition to a unit missing Gerald McRath, he returns from a four-game suspension Monday, and veteran David Thornton, who's on the physically-unable-to-perform list recovering from hip surgery. Bulluck wound up signing with the Giants in July.
Safety Chris Hope, who's been in Tennessee since 2006, said Witherspoon is having fun. He credits the 6-foot-1, 240-pound linebacker with being smart with lots of experience in big games.
"He's been here all offseason. He's studied. He's been in that meeting room with the linebackers and with coach Mc," Hope said of linebackers assistant coach Dave McGinnis. "It's not a surprise he's picked it up so fast."
The Titans haven't had a player pick up a sack in four straight games since Jevon Kearse in 2003 when they last won a playoff game. Witherspoon already is just four sacks shy of his career-best seven sacks with St. Louis in 2007 and has 23 for his career, and he calls his sacks the result of great calls for the plays opponents had dialed up.
"I've never considered myself a great blitzer. I guess I'm an all right blitzer. I have enough sacks to prove that at this point. It's just great calls have come at the right time," Witherspoon said.
The Titans haven't blitzed much, but Fisher said Witherspoon has gotten through clean when they have sent the linebacker.
"He's got a good sense of timing," Fisher said.
The Titans too based on Witherspoon's play.