CHARLOTTE, N.C. -- The Carolina Panthers have added more depth to their already deep stable of running backs.

The Panthers announced Monday they've signed free agent Mike Tolbert from the San Diego Chargers. Tolbert spent three seasons with Ron Rivera, who was the Chargers' defensive coordinator before becoming the Panthers' coach.

"Mike is a very versatile player who can do a lot of different things for us," Panthers general manager Marty Hurney said in a release. "He plays fullback, catches the ball well out of the backfield, plays running back, and is an outstanding special teams player."

Tolbert's agent Joel Turner said his client signed a four-year contract, but would not disclose the financial terms of the deal.

However, he said Tolbert was so excited about joining Carolina that he left over $1 million on the table on an offer from San Diego.

"That's how bad he wanted to play there," Turner said. "He loves the idea of playing for Ron Rivera and being on the same team with Cam Newton. He just thinks it's a great fit."

Tolbert has spent all four of his seasons in the NFL with San Diego. He had 490 yards rushing and 433 yards receiving on 54 catches last season and scored 10 touchdowns while splitting time with Ryan Mathews. His best season came in 2010 when he led the Chargers with 735 yards rushing and 11 touchdowns.

Tolbert has started 15 games and played in 59 during his four years with the Chargers.

A former player at Coastal Carolina, Tolbert was eager to get back to the East Coast and liked what he saw from the Panthers organization, Turner said.

The question now is what this means for the rest of Carolina's backfield.