Royal hurt his hamstring in the Bills' win at Kansas City on Sunday and didn't practice all week. Greer's right knee was injured against Cleveland two weeks ago and he'll miss his second straight game.
Backup defensive lineman John McCargo was placed on injured reserve because of a back injury. His trade to Indianapolis earlier this season was voided after he failed his physical with the Colts because of a reported bulging disk in his back.
Backup linebacker Teddy Lehman (hamstring) are out, while starting linebacker Keith Ellison (ankle) and tight end Derek Schouman (hamstring) are questionable.
Tight end Jonathan Stupar was promoted from the practice squad to the Bills 53-man roster to replace McCargo.
Copyright 2008 by The Associated Press