SANTA CLARA Backup defensive end Demarcus Dobbs was arrested early Friday after he was involved in a solo car crash.
The California Highway Patrol said driving under the influence was suspected and that Dobbs, who turned 25 Friday, was arrested for marijuana possession.
Officer D.J. Sarabia said the incident occurred at 3:45 a.m. on southbound San Tomas Expressway in Santa Clara, where the 49ers have their practice facility and are building their new stadium.
Sarabia said Dobbs was driving a 2011 Cadillac. He was not injured in the accident, and no one else was in the car. Sarabia said Dobbs agreed to a chemical test, the results of which have not yet been determined.
The 49ers have declared him out of Sunday's game against the Rams, and Dobbs will not travel to St. Louis.
"The 49ers are aware of the recent matter involving Demarcus Dobbs," the team said in a statement. "We are gathering the relevant facts as it pertains to this situation. We have been in contact with both Demarcus and the league office. He will not be making the trip to St. Louis, and we will reserve further comment at this time."
Dobbs, who made the squad in 2011 after going undrafted out of Georgia, plays defensive end and tight end and is a core member of the 49ers' special teams. He tops the statistical chart maintained by special-teams coordinator Brad Seely.
Dobbs backs up Justin Smith at right defensive end, a role that likely will be filled by Will Tukuafu on Sunday.
Dobbs is the second 49ers defender to be arrested this year. NFL sack leader Aldon Smith was arrested on suspicion of DUI in Miami in January. He qualified for a program to reduce the charge to reckless driving.
Smith also was stabbed at a house party in June and was involved in a rollover car accident in September.