How good can Cam Newton be?

Cam Newton has been phenomenal so far in his rookie season for the Panthers. Streeter Lecka/Getty Images

Carolina Panthers quarterback Cam Newton only threw for 171 yards against the Tampa Bay Buccaneers on Sunday, but that was all he needed to set his latest benchmark. Newton now has 3,893 passing yards this season, breaking Peyton Manning's rookie record of 3,739 set in 1998. Newton also has 14 rushing touchdowns, the most for any quarterback in a single season, rookie or otherwise. So the obvious question becomes: Have we ever seen anyone -- or anything -- like this?

Frankly, no. At Football Outsiders, we use similarity scores to find historical matches for contemporary players. (Similarity scores were invented by baseball analyst Bill James and have since been used by many other statisticians for many other sports.) Our formula uses not just on-field performance, but also factors such as size, age and experience in an attempt to predict each player's future.

Newton essentially breaks our similarity score system. He's on pace for 719 rushing yards. The only quarterbacks who have rushed for more than 700 yards since the merger are Michael Vick, Bobby Douglass and Randall Cunningham. (Vick has done it three times and can make it four with 114 yards against Washington next week. Tim Tebow needs 56 yards against Kansas City to join the club.) The system doesn't know what to do with all that ground yardage and tries to match up Newton with occasional scramblers, such as Mark Brunell and Don Majkowski.

Newton's rushing ability is no fluke, and at 6-foot-5 and 248 pounds, there's no reason to expect his numbers on the ground to dissipate anytime soon. To get a better picture of his performance, let's separate his passing stats from his rushing stats. Since we can't find anyone who could run and throw like Newton, let's start with players who threw like him, then look for those who ran like him.

Projecting Newton's stats over 16 games gives us 315 completions, 525 attempts, 4,153 yards, 21 touchdowns and 17 interceptions, all at the tender age of 22. Here are the 10 quarterback seasons most similar to that since 1978: