ALAMEDA, Calif. (AP) -- Oakland Raiders running back Dominic Rhodes was suspended Tuesday for the first four games of the season for violating the league's substance abuse policy.

The league does not disclose reasons for substance abuse suspensions, but Rhodes pleaded guilty in the offseason to reckless driving charges in Indiana after prosecutors agreed to drop drunken driving charges against him.

Rhodes, who spent his six years in Indianapolis, signed a two-year contract in the offseason with the Raiders that could be worth up to $7.5 million. He is expected to split time with last year's starter LaMont Jordan as the Raiders try to improve a running game that averaged 3.9 yards per carry in 2006.

Rhodes started all 16 regular-season games last season, rushing for 641 yards and five touchdowns. After backing up Edgerrin James since entering the league, Rhodes shared the job last season with rookie Joseph Addai. He has 2,274 yards rushing in his career.

Rhodes had one of his best performances in the Colts' Super Bowl win over the Chicago Bears, rushing for 113 yards in Indianapolis' 29-17 victory.

Rhodes will be able to participate in training camp and in all preseason games. His suspension will begin Aug. 31, the day after Oakland's final exhibition game, and he will be eligible to return Oct. 1, following the fourth game of the season against Miami. Rhodes will also miss games against Detroit, Denver and Cleveland.

Rhodes was pulled over by an Indiana state trooper in February for driving 81 mph in a 55-mph zone. He was originally charged with operating a vehicle while intoxicated and operating a vehicle with a blood-alcohol level above the legal limit.

Rhodes pleaded guilty in March to reckless driving and was sentenced to 180 days in jail. But 178 were suspended and he received credit for two days.

In 2002, Rhodes was charged with domestic battery in connection with a disturbance at his home involving his child's mother, Latrina Moore. He avoided prosecution and was placed in a diversionary program and underwent mental health counseling.