On Wednesday, Oakland delivered the news that Kelly's season is over and that the team will likely put him on injured reserve within the next 24-48 hours.
"The last two games he had played extremely well and was making some plays," Raiders coach Lane Kiffin said. "It's unfortunate."
Kelly is in the final year of his contract with Oakland. Though there were preliminary talks about an extension, no deal ever materialized.
Because of his versatility, Kelly -- who earned $1.35 million this year in base salary -- will be among the most coveted free agents in the offseason, though Kiffin is optimistic Kelly will return.
"Hopefully we'll have Tommy back as a Raider for next year," Kiffin said, "and years to come."
Replacing Kelly next year is a decision management doesn't have to worry about now. But there is a serious concern over how they fill the void left by his absence this season. With defensive tackle Gerard Warren still not practicing, the Raiders are in a bind across their defensive line.
"It's something we're going to have a hard time doing but we've got great players behind Tommy, and whether it's one or two guys to have to fill that multiple role that Tommy played, then that's what it'll be," Oakland defensive coordinator Rob Ryan said. "It's unfortunate we lose a great player like that. That's something that happens in this league and it's a shame. But just like anybody else, you've got to step up with the next man."
The Raiders already have one defensive tackle, Josh Shaw, on their practice squad. They added another with the signing Wednesday of Jonathan Lewis, a sixth-round draft pick of Arizona's in 2006. Lewis played sparingly as a rookie before being released by the Cardinals at the end of the preseason this year.