The attorney for 23-year-old Andrew Thomas Gallo says the publicity surrounding the April 9, 2009, crash will make it hard for Gallo to get a fair trial.
Gallo has pleaded not guilty to three counts of murder and other felonies in the crash that killed Adenhart and two friends.
Police say Gallo had nearly triple the legal blood-alcohol level when his minivan ran a red light and crashed in Fullerton.
Adenhart died hours after he made his season debut by pitching six scoreless innings.
Superior Court Judge Richard Toohey scheduled a May 28 hearing on the motion and also pushed back Gallo's previous April trial date to July.