Null not only backup QB in game

Titans quarterback Vince Young was running freely -- perhaps too freely -- through the Rams' defense.

He pulled up toward the end of the run and clutched the top of his right hamstring.

Young gained 44 yards on the play. He probably could have fought for more if the injury did not force him to the sideline. Kerry Collins is in the game at quarterback for Tennessee.

A game featuring top running backs Chris Johnson (two touchdowns already) and Steven Jackson also features two backup quarterbacks.

Rookie third-stringer Keith Null started for the Rams. Collins is now leading the Titans.

Null has passed for only 50 yards on 15 attempts, but he has avoided sacks and costly mistakes.