"The adrenaline was rushing and I learned a lot of new stuff," Mathews said Sunday night, hours after signing a five-year, $25.65 million contract, with just more than $15 million in guaranteed money. "Everyone is going 100 miles an hour -- safeties, linebackers coming at you a little harder in pads. It's football and I love to play it. It's all fun."
Mathews missed seven practices, including three for rookies and selected veterans last week.
"I've got a little bit of making up to do, but that will happen in the next couple of days," he said.
Mathews is San Diego's first new featured running back since Tomlinson was a rookie in 2001. Tomlinson missed most of training camp that year during a holdout, but he ran for 113 yards and two touchdowns in the season opener.
"Myself, I'm just here to help the team win," Mathews said. "That is the No. 1 thing why they drafted me. That is all I can say. My role on the team is just to run the ball and help the team do what it can to get to the last game of the year."
Mathews rushed for 3,280 yards in three seasons at Fresno State, scoring a school-record 39 touchdowns and averaging 6.1 yards per carry. Last season, as a junior, he rushed for 100 yards against three Top 25 teams -- Cincinnati, Boise State and Wisconsin. He ran for 234 yards against Boise State, scoring on runs of 69, 60 and 68 yards.
NFL Network insider Jason La Canfora reported Friday that the team had begun discussions with representatives for left tackle Marcus McNeill. Linebacker Shawne Merriman told The Union-Tribune on Thursday that he wouldn't report to camp on time, citing the need for security from team management. The Chargers don't want to trade disgruntled wide receiver Vincent Jackson but have possible suitors in the Washington Redskins and Seattle Seahawks, La Canfora reported Friday.
The Associated Press contributed to this report.