Buffalo Bills head coach Chan Gailey told reporters after practice on Thursday that veteran defensive tackle Spencer Johnson will miss Week 5 against the San Francisco 49ers with an ankle injury.

Johnson, the team's third defensive tackle that gets onto the field for about one-third of the team's snaps on a good weekend, has been playing through said ankle injury - and it's gotten worse to the point that the coach now believes it's as bad as the ankle injuries that will keep offensive linemen Cordy Glenn and Kraig Urbik from playing for the next couple of weeks.

That means that one week after allowing the New England Patriots to run for 247 yards in a resounding defeat, the Bills will be playing a run-first 49ers outfit with three defensive tackles on the active roster: Kyle Williams, Marcell Dareus and Alex Carrington. Keep in mind, also, that Dareus has been fighting through an ankle injury for the last couple of games, and was spotted limping off of the field against the Patriots numerous times.

The news is not all bad, however: free safety Jairus Byrd (hip) returned to the practice field on Thursday after sitting out Wednesday. Even though he was limited today, he's still on track to man his starting safety spot on Sunday.

Glenn and Urbik did not practice for a second straight day, and they've already been ruled out for Sunday, as well. Wide receiver Ruvell Martin was a limited participant for a second straight day, and Gailey is hopeful that he'll be available on Sunday to get back to his special teams role. Donald Jones and Scott Chandler, who both got dinged against the Patriots and were listed as full participants on Wednesday, have been removed from the injury report.