Rams starting cornerback Derion Kendrick was arrested in Los Angeles on Monday ... less than 12 hours after he helped his team beat the Arizona Cardinals.
Law enforcement sources tell TMZ Sports ... the 23-year-old was pulled over early in the morning for a traffic violation -- and we're told during the stop, police found a gun in his car.
Jail records show Kendrick was then booked at 2:14 a.m. on a felony charge of carrying a concealed weapon ... and as of 2:30 p.m. on Monday, he remained in custody.