Pierce (concussion) has been ruled out for Sunday's game against the Rams, Amanda Foster of the Colts' official site reports.
At this stage, Pierce remains in the NFL's concussion protocol, so his next chance to see game action will arrive Sunday, Oct. 5 against the Raiders. In Pierce's absence Sunday, Adonai Mitchell figures to see an expanded Week 4 role alongside fellow WRs Michael Pittman and Josh Downs.