If you have not already seen my article on Xavien Howard vs. Tony Lippett, I suggest you take a look before continuing on, as this will be a brief recap of Lippett's stats. Those stats include open spaces, too many out-cuts, but he adjusts well to pressure and he was team MVP and finished 2014 as starting wide receiver and starting cornerback.
McCain is very fast, he can pivot and flip with the best of them and he always makes a burst for the ball, he is able to click and close to limit yards after catch, he grabbed 11 interceptions over the last two seasons. His downside is his size, the reality is that he is not a big guy and does not compare to other CB's that way which is a bit harder for him because he is immediately overpowered.
Ajayi is the last out of the three, as an English native American football was not his first love and he did not start to play until 2003 after moving to the States in 2000. But, it won out and he decided to try it professionally. His stats include running into defenders he should be able to avoid, a heavy workload in 2014 with 398 total touches (28.4 per game), and a small criminal record. But, because he used to play soccer he has quick feet and quick thinking, he has good hands and an ability to maximize each catch in space, along with being able to come up with multiple move decisions at the same time.
I think all three guys have a lot of potential to break out. They have their hang-ups but with a little more practice they all have a chance to become NFL starters.