DAYTONA BEACH, Fla. (AP) - Rain washed out the final two practices before NASCAR's season-opening Daytona 500.

It's a potential setback for the nine drivers switching cars before "The Great American Race.''

Former Cup Series champions Brad Keselowski and Martin Truex Jr. as well as front-row qualifier William Byron are among those forced into backup cars because of issues in the 150-mile qualifying races Thursday night.

Erik Jones, Chase Briscoe, Kaz Grala, Anthony Alfredo, Cole Custer and Ross Chastain also switched cars and will have to start Sunday's race from the back of the 40-car field.