If there’s one simple statistic that predicts how well both a quarterback and his team will fare in terms of wins and losses, it’s passing yards per attempt (YPA). No other stat is as consistent and predictive of winning in the NFL. So how should we evaluate Robert Griffin III’s preseason numbers? How does his 6.2 YPA stack up, and what does it signify?

It’s solid, right in the pack of rookie starting QBs over the past five seasons, many of whom panned out into solid franchise QBs. Unfortunately, all of that means nothing. Of the 22 rookie QBs who started for their teams and who had at least 100 pass attempts in their rookie regular season, the correlation coefficient between preseason YPA and regular season YPA is -0.20. (A correlation coefficient is a number between 1 and -1 that indicates how closely two sets of numbers are related.) A correlation of -0.20 means that the better a QB does in the preseason the worse he tends to do in the regular season!

In truth, what this really means is that there is no meaningful connection between preseason and regular season performance. The preseason simply doesn’t provide enough information to draw any inferences. There are too few attempts, and the schemes are too vanilla. The QBs sometimes face starters and sometimes face third stringers.

The worst rookie preseason performers of the past five seasons include Joe Flacco (4.2 YPA), Matt Ryan (5.0 YPA), and Cam Newton (5.3 YPA). The best rookie preseason performances include Bruce Gradkowski (8.4 YPA), Mark Sanchez (8.1 YPA), John Skelton (8.1 YPA) and Trent Edwards (7.1 YPA). So even Andrew Luck’s phenomenal 7.9 YPA this preseason may not amount to much.

Only the Redskins’ coaches know whether Griffin read defenses correctly, went through his progressions properly and made the play that was called. But I’m not sure even they can make a reliable assessment. Griffin was only given 31 pass attempts in the preseason, ranking 75th among all league passers. That’s only about one full regular season game worth of passes. You’d think that the team would want the player on whom they’ve bet the franchise to get more experience before the bullets are real.

It makes sense that with a rookie QB and a stout defense the Redskins will lean on their running game this year. But why do that in the preseason? Coach Mike Shanahan’s zone blocking scheme is known for its simplicity and has been installed for two full years. Protecting Griffin from injury might be one reason to limit his exposure, but if things go according to plan, he’ll have hundreds of drop-backs this season and be just at risk of injury in each one. In comparison, Luck ranked 10th with 66 attempts this preseason, more than twice as many as the Redskins gave Griffin.

We just don’t know what to expect from Griffin this season, and with only 31 attempts in four games, it’s hard for his coaches to know what to expect either.

Brian Burke is the creator of Advanced NFL Stats, a Web site about football, statistics and game theory.