Darnold got a 7.0 rating, and Mahomes a 5.8. Rosen is a 6.1, and both Mayfield and Allen are 6.0. My understanding, however, is that while the difference between 5.8 and the low 6s may seem small, it's considered pretty relevant. 6.0 is the cutoff for a presumptively good starter. Below that, the projection gets dicier.