Projecting booms, busts among top 2018 QB prospects

There are no sure things in the NFL draft, but quarterback may be the riskiest position of all. No defense revolves around a single player the way every offense revolves around the quarterback. Trust your offense to the wrong young quarterback, and your team isn't going to climb back into playoff contention. Recent history is littered with teams that drafted a quarterback high, only to find out that player couldn't play at the NFL level.

The lessons of history can at least help us figure out how much of a risk each quarterback prospect will be. That's the point of Football Outsiders' Quarterback-Adjusted-Stats-and-Experience (QBASE) projection system. It looks at college performance, experience and expected draft position (to incorporate scouting information that college stats will miss). To allow some time for development, QBASE projects a quarterback's efficiency (passing only) in Years 3-5 of his career, according to Football Outsiders' defense-adjusted yards above replacement (DYAR) metric. 50,000 simulations produce a range of potential outcomes for each prospect, with players drafted later generally having a larger range of possibilities.

QBASE favors quarterbacks expected to go high in the draft who also have a relatively long résumé of college success according to the stats. Those stats include completion percentage, yards per attempt and team passing efficiency. These numbers are adjusted both for the quality of the defenses that a prospect had to face as well as the quality of his offensive teammates. QBASE is meant to only be used on players chosen in the top 100 picks; after that, the judgment of scouts becomes even more important, and statistics become even less predictive.

It's important not to overestimate the importance of a small difference in the QBASE projections. Most of this year's top quarterbacks are grouped together in the middle of the scale. It's a bit of a surprise that Sam Darnold came out with a lower QBASE rating than some of the other top prospects -- Josh Rosen, for example. But if I were the analytics director for an NFL franchise, I would feel no need to disagree with a scouting director who placed Darnold ahead of Rosen.

However, there is one top prospect who QBASE clearly likes ahead of all the others, and one top prospect whose statistical profile is a gigantic red flag. We explain both projections below, along with the QBASE projections for six other top quarterbacks based on Scouts Inc. rankings for the 2018 draft.