Mathews, the heir apparent to LaDainian Tomlinson, is San Diego's only draft pick who hasn't signed a contract. He was taken with the 12th pick overall out of Fresno State.
Rookies and selected veterans will practice through Thursday, when the rest of the veterans are due to report. The first full-squad practice will be Friday.
Pro Bowl wide receiver Vincent Jackson and left tackle Marcus McNeill are expected to miss training camp and possibly the first 10 games of the season. They are unhappy they haven't been signed to long-term deals. It's also uncertain when outside linebacker Shawne Merriman will report.
Copyright 2010 by The Associated Press
Forlan eyes Prem returnKevin Ellison, arrested last month, cut by San Diego Chargers