Here's a good story. An injury forces the starter to step aside. A young replacement emerges from the shadows and leads the team to victory.

It may be a good story, but not a likely one.

Not when the position is quarterback. Not when the opponent has the top-ranked defense in the nation.

If destiny -- in the form of Erik Ainge's sprained ankle -- brings Jonathan Crompton out of the shadows Saturday against LSU, he won't be the first Tennessee quarterback to face such a challenge/opportunity.

Injuries are part of the game and that goes for quarterbacks, too. But given the track record of LSU's defense, Crompton's challenge, if it comes, will rank up there with the toughest.

And, frankly, history suggests happy endings are few and far between under circumstances such as these.

Tennessee has been relatively lucky with keeping its starting quarterbacks healthy over the years.

A famous exception was 1985, when Tony Robinson went from a Sports Illustrated cover to crutches in a matter of weeks.

Yes, Daryl Dickey emerged from the shadows and led the Vols to one of the happiest endings in school history: an SEC title and Sugar Bowl romp over Miami.

But Dickey didn't hit the ground running. In his first start, it took a 51-yard field goal with four seconds to play to salvage a 6-6 tie with Georgia Tech.

Dickey didn't face another first-rate defense until Miami, and by then he'd had five games to get up to speed.

In the 21 years since the Sugar Vols, Tennessee has had to scramble here and there to fill in for an injured quarterback.

In those scrambles, only one time has a replacement quarterback guided the Vols to victory over a ranked team.

That was 1994. Starter Jerry Colquitt went down seven plays into the season-opener. Tennessee lost to UCLA that day but a week later Todd Helton quarterbacked a 41-23 win over No. 23 Georgia.

Two weeks later, Helton was also injured at Mississippi State and a freshman named Peyton Manning emerged to ...

Watch the Bulldogs rally for a 24-21 victory that dropped the Vols to 1-3.

In 1987, starter Jeff Francis was hurt in late October. So Randy Sanders pounced on his second chance and ...

Struggled and was replaced by third-stringer Sterling Henton in a loss at Boston College.

Henton went on to direct blowout wins over Louisville and Ole Miss. Neither of those teams, however, is comparable to 2006 LSU.

When a fractured collarbone knocked Casey Clausen out of the lineup in 2002, transfer C.J. Leak jumped at his golden opportunity and ...

Lasted only two series at No. 6 Georgia before James Banks came in and finished an 18-13 loss.

When a sprained ankle knocked Clausen out of the lineup a month later, Banks filled in again with better results, a 35-17 win against a weak Mississippi State team.

Tennessee ran the ball on 64 of 72 snaps that day, an option not likely to present itself Saturday.

The most recent chapter was 2004, when Ainge suffered a separated shoulder on the final play of the first half against Notre Dame.

Rick Clausen emerged from those shadows and ...

Threw an interception that Notre Dame returned for a game-winning touchdown in a 17-13 upset.

Once past that stumble, Clausen acquitted himself admirably as the Vols beat Vanderbilt and Kentucky.

And like Dickey 19 years earlier, given a couple of games to get acclimated, Clausen ended up the MVP of a bowl victory.

This week, though, is different.

Ainge's injury isn't season-ending. Crompton isn't looking at a month to get acclimated for a bowl game. What the Vols need here is a pinch-hitter to come off the bench swinging.

If he gets the call Saturday, Crompton will have several things going for him. He'll have a crafty play-caller. He'll have an offensive line that protects its quarterbacks. And from what little we've seen, he's got more talent than the average backup.

However, the bad timing of facing the nation's stingiest defense will be working against him.

So will history.