The Jets also released wide receiver Chris Owusu.
Walls, who has started seven of the Jets' eight games this season, was listed as doubtful Friday because of calf and knee injuries. The Jets announced Saturday that he won't travel with the team to Kansas City. Phillip Adams could start in his place.
Simms will serve as insurance behind starter Michael Vick in case backup Geno Smith is not available. Smith is questionable with a sore right shoulder, suffered before being benched in the Jets' 43-23 loss to Buffalo last Sunday.
Owusu had one catch for 7 yards with the Jets.