CHARLOTTE, N.C. (AP) – Mike Trgovac became the fourth assistant to leave Carolina coach John Fox’s staff since the Panthers’ upset playoff loss to Arizona, adding more uncertainty to what has already become a tumultuous offseason.

Team spokesman Charlie Dayton said Thursday that Trgovac informed Fox and general manager Marty Hurney of his decision at Senior Bowl practices in Mobile, Ala. The move came after the Panthers had offered their defensive coordinator a contract extension.

Hurney did not immediately return a phone message seeking comment. Trgovac, who had just finished his seventh season with the team, could not be reached.

Defensive ends coach Sal Sunseri, a close friend of Fox, left for Alabama after seven seasons with the Panthers. Linebackers coach Ken Flajole also left this week after six seasons in Carolina to become defensive coordinator of the St. Louis Rams.

Quarterbacks coach Mike McCoy, who had spent nine seasons with the Panthers, was hired as the Denver Broncos’ offensive coordinator.

All of the assistant coaches were working under contracts that expired after this season. The team is trying to secure new deals with the rest of the staff, including offensive coordinator Jeff Davidson.

The Panthers are also close to hiring former Cleveland Browns quarterbacks coach Rip Scherer to replace McCoy.

Trgovac joined Fox’s staff in 2002 as defensive line coach and was promoted to defensive coordinator a year later, when Jack Del Rio left to coach the Jacksonville Jaguars.

The Panthers struggled on defense late this season, giving up 30 or more points in six of their last seven games, including a 33-13 home playoff loss to Arizona that came on the heels of a 12-4 regular season.

Fox, a former defensive coordinator with the New York Giants, had given Trgovac strong public support and the two sides had discussed a two-year contract extension this week.

It’s unclear how Fox will replace Trgovac, and whether that decision might make defensive end Julius Peppers reconsider his decision to want out.

Peppers’ agent, Carl Carey, said last week that Peppers would not sign a long-term deal with the Panthers when he becomes an unrestricted free agent next month. The Panthers could still place the franchise tag on Peppers, which would virtually guarantee he’d stay at Carolina in a one-year deal worth about $16.7 million.

Carey has said Peppers, who had a career-high 14O sacks this season and made his fourth Pro Bowl, was looking to play in a different defensive system so that he could “reach his full potential.”

Carey did not return a phone message Thursday seeking comment.