Mattias Ekstrom is driving the car Sunday at Infineon Raceway, and RBR announced Reed Sorenson will drive next week at New Hampshire.
"Our unique situation has afforded us the opportunity to try some different things, and we're continuing to do that with Reed," RBR general manager Jay Frye said in a statement. "We appreciate Casey's work and everything he's done the past five weeks."
The contact with Speed drew harsh words.
"Both of us were struggling but [Mears] wrecking us like that -- I mean is ridiculous," Speed told reporters after the race. "Whenever you're at Hendrick [Motorsports] and Richard Childress Racing and then you still don't have a ride and haven't done anything there's no real excuses after that, but whatever.''
In four starts since Vickers was ruled out for the rest of the season because of blood-clot treatment, Mears finished 22nd, 29th, 23rd and 36th.
Sorenson made three races this season for Todd Braun, finishing 39th, 41st and 43rd.
David Newton covers NASCAR for ESPN.com. He can be reached at email@example.com.