INDIANAPOLIS -- All-Pro linebacker Darius Leonard has been ruled out and receiver T.Y. Hilton is doubtful for the Indianapolis Colts' game against the Oakland Raiders on Sunday, coach Frank Reich said Friday.

Leonard, who led the NFL in tackles (163) as a rookie in 2018, hasn't practiced since he suffered a concussion in the team's Week 2 victory at the Titans. He will remain out until he passes the NFL's concussion protocol.

Rookie Bobby Okereke will continue to start at middle linebacker with Anthony Walker, who normally starts in the middle, playing on the outside for the second straight week.

Hilton injured his quadriceps late in the first half against the visiting Atlanta Falcons last weekend. He remained in the game several more plays, catching a 4-yard touchdown, before heading to the locker room in the final seconds of the half and then sitting out the final two quarters.

Hilton did said Friday he's "ahead of schedule" and that his quad is "feeling better."

With Hilton doubtful, the Colts elevated receiver Ashton Dulin from the practice squad to the 53-man roster and waived cornerback Ryan Lewis.