Ok, but for the record I don't think I'm the only one who has said Whitlock has the best stuff of all those guys, although I think an argument could be made for Bello in terms of pure stuff. Whitlock hasn't proven himself as a starter because he hasn't really been used as a starter, but for what information we have.....he's been better than those other guys.
As a starter ERA WHIP
Whitlock 4.15 1.25
Crawford 3.70 1.09
Wink 4.69 1.49
Bello 8.47 2.29
You can say Crawford has proved himself more in short sample size, also Whitlcik beats out everyone else in peripherals as well H9/BB9/K9
Whitlock, also performed much better in the MiLB than those guys.
ERA/WHIP/H9/BB9/K9
Whitlock 2.45/1.175/8.0/2.5/8.8
Crawford 3.73/1.28/8.5/3.1/10.6
Wink 3.89/1.245/8.5/2.7/8.2
Bello 3.92/1.177/7.9/2.7/10.9
From a pure statistical point of View Whitlock beats everyone out except Crawford at the MLB level and Bello at the minor league level, GW has shown a lower era and slightly better control but Bello has had more swing and miss stuff. Body types, durability, developing 3rd/4th pitches and how that can change stats from milb to MLB are all things to consider to.
I think a very strong argument should be made for Whitlock being in the rotation. I think the Sox believe so too, which is why they are using him the way they are.
Another thing worth stating too is it shouldn't be Whitlock vs. anybody. If a guy is good enough to start, he should be starting....that's where he adds the most value. If you have too many starters, trade one for a proven reliever.