What is IR (injured reserve) in fantasy football?
IR (Injured Reserve) is a special roster slot where you can stash an injured player so he doesn't take up an active bench spot.
An IR slot lets you keep an injured player on your roster while freeing up a bench spot to add a replacement.
If your star receiver lands on the NFL's injured reserve, you can move him to your fantasy IR slot, which opens a roster spot to grab a waiver-wire fill-in. Most platforms, including Sleeper, require the player to carry an official injury designation (like IR, Out, or sometimes Questionable) to be eligible. When he's healthy again, you move him back to your active roster.
IR slots are a roster-management tool, not extra starters — players parked on IR can't be put in your lineup. They simply let you hold injured talent without sacrificing depth.