If the Titans are going to make it to an improbable 9-7 finish, they must do it with two inexperienced linebackers in their base defense.

Keith Bulluck, who’s started 127 consecutive games, is out for the year with a torn ACL in his left knee. David Thornton, who has battled a shoulder injury in recent weeks, is also finished, Jeff Fisher said Monday at his news conference. Thornton will have shoulder and pectoral surgery in the next few days.

Bulluck’s been a defensive stalwart for the team and is heading for unrestricted free agency. If the injury suffered Sunday against the Dolphins was his final moment with the Titans, it’s a sad ending.

A speedy linebacker who has been especially good in coverage, he has also served as a no-nonsense team spokesman since early in his tenure as a starter.

Without him or Thornton, the team is OK with rookie Gerald McRath. But now Colin Allred’s in line to start in a trio led by middle linebacker Stephen Tulloch, who will stay on the field in nickel situations. Second-year man Stanford Keglar is the primary backup.

That’s a significant downgrade to the Tennessee defense.

The Titans face San Diego at LP Field Christmas night before finishing at Seattle. Two wins could get them to 9-7 after an 0-6 start, but they’d also need a bunch of help because their poor conference record won’t help them in playoff tiebreakers.

Bulluck was the team’s leading tackler with 113 with three tackles for a loss, three interceptions, eight passes defensed and a fumble recovery.

He posted these three messages on his Twitter account (@kbull53) this afternoon:

"Yo so y'all heard the news torn ACL...after 127 str8 games u already kno I ain't go'n out like this. My spirits r gr8 thanx 4 the love cont."

"and support all this year."

"I think my rehab hobby is gonna be to finally learn to play my guitar..."