The discussions about Crow needing to develop a 3rd pitch got me thinking about Major League starters who don't have a good third pitch, or at least don't use it much. Out of 108 qualifying starters, five use two main pitches more frequently than Crow uses his fastball and slider. I've listed the pitchers and their 3rd pitch usage below.
Michael Pineda - 5.8% - CH
Alexei Ogando - 4.8% - CH
Ervin Santana - 3.1% - CH
Justin Masterson - 0.9% CU
Gio Gonzalez - 5.9% - CU
Excluding the lefty Gonzalez, the other 4 are effective RH pitchers with plus fastballs and sliders, similar to Crow. My opinion is that this number would be higher if pitchers with effective fastball-slider combinations and a limited 3rd pitch weren't relegated to BP duty early in their careers
My point is that I don't think the Royals have screwed up the development of Aaron Crow. His command of his two good pitches will determine whether he's a MLB starter or not, not the development of a weak but usable 3rd pitch, and he has had a good chance to work on that this year at the MLB level.