Sorry to be late on this. The Colts must be more than a tad worried about Josh Chapman's availability because they signed another nose tackle. Jason Shirley (6051/329/5.02pd in 2008) has had something of a colorful past. He's been around (playing for the Bengals, the Seahawks and the Panthers before landing in Indy), played a little (he had 2.5 sacks for the Bengals before they switched him to guard) and he's been in trouble (served a month after a drunken hit-and-run incident).
Shirley offers little other than size and strength, and perhaps a little experience.