Rob Ryan tries to replace Kenyon Coleman

IRVING, Texas -- One of the first free-agency signings with Rob Ryan as the defensive coordinator last year was defensive end Kenyon Coleman.

In his second season, Coleman suffered a season-ending triceps injury that will cost him the final seven games of the 2012 season.

The Cowboys will replace Coleman with Marcus Spears on run plays and Tyrone Crawford in passing situations.

"Kenyon is a great player. Some people don't realize how important he is to us," Ryan said. "He's a great run player and a great leader. It's tough, I won't be crying about all these injuries, but man, I might start."

Ryan's defense missed starting nose tackle Jay Ratliff the first four games of the season with an ankle injury, lost starting safety Barry Church to a torn Achilles in September, inside linebacker Sean Lee to a toe injury in October and at times haven't had cornerback Mike Jenkins (back), linebacker Dan Connor (neck) and defensive end Sean Lissemore (ankle).

"It's been a hard year for us," Ryan said. "We've got the great Marcus Spears ready to go, so we're fortunate to have an excellent player behind Kenyon. We need Lissemore back, but he's out a few more weeks. We're going to do the best we can. Marcus is a helluva football player and he's going to step up, but (Coleman's) a guy you never truly replace."