The receiver needs to pass concussion protocol this week to be eligible to play Sunday against the Pittsburgh Steelers.
If Maclin can't play Sunday it's another big blow to the Chiefs' offense, which is already without its top player, Jamaal Charles, who is out for the season with a torn ACL.
Maclin is quarterback Alex Smith's top target, compiling 39 receptions (eighth-most in the NFL) on 56 targets for 531 yards and a touchdown grab. Albert Wilson and Chris Conley likely will be the top receiver targets if Maclin can't play, with tight end Travis Kelce as Smith's go-to pass-catcher.
The banged-up Chiefs also practiced without Mike DeVito (concussion) and Tamba Hali (knee) Wednesday.