Updated

"NASCAR Race Hub" co-host and longtime NASCAR on FOX on-air personality Steve Byrnes will take a medical leave of absence for the remainder of the 2013 NASCAR season, effective immediately.

Adam Alexander, one of the show's original hosts, will fill in for Byrnes alongside Danielle Trotta beginning with the Sept. 30 edition (4 p.m. ET, FOX Sports 1). "NASCAR Race Hub" has returned to a one-hour format through the completion of the 2013 season in order to highlight the Chase for the NASCAR Sprint Cup.

Any updates on Byrnes will come at the discretion of the family.