(AP Photo/Nick Wass)

There was a ton of optimism after it was announced that Jay Gruden would be the new head coach for the Washington Redskins. Gruden brought new life to the Cincinnati Bengals’ offense, where he served as offensive coordinator the past three seasons, and everyone foamed at the mouth over what he could do with a talent like Robert Griffin III under center.

There is only one problem: We likely have seen the best RGIII will ever be.

During his rookie season, Griffin threw for 3,200 yards and 20 touchdowns with just five interceptions, earning AP offensive rookie of the year honors. His adjusted net yards per attempt — introduced in The Hidden Game of Football by Bob Carroll, Pete Palmer and John Thorn — was a robust 7.47, or 20 percent better than the average. Adjusted net yards per attempt “is a souped up version of your basic Yards per Pass Attempt stat that reflects both the reality of today’s NFL and the importance of passing efficiency in the modern game,” says one analyst.

Adjusted Yards gained per pass attempt = (Passing Yards + 20 * Passing TD – 45 * Interceptions) / (Passes Attempted)

In the history of the NFL, there have been only three other quarterbacks since the merger to be as much or more above the league average than Griffin in their debut season (minimum 100 passing attempts): Pat Haden (1976), Dan Marino (1983) and Marc Bulger (2002). Only Marino would hit or exceed the mark again.

When we look at all quarterbacks — rookie or not — who have posted seasons in which they were 20 percent above the league ANY/A average, we find that most don’t have a repeat performance. And if they do, there is no telling when it will happen.

Neil Paine from FiveThirtyEight came to a similar conclusion using Pro Football Reference’s Approximate Value. Just 35 quarterback seasons since 1950 were better than Griffin’s 2012 campaign, which leads Paine to give a one in three chance Griffin would ever surpass his 2012 season — even before the knee injury.

This isn’t to say Griffin can’t win games or be a good quarterback for Washington over his career, just that expectations really do need to be tempered down for the foreseeable future.