Doyle, a starting pitcher without electric stuff and who had only pitched a half season at AA, wasn't a likely candidate for an opening day roster spot, even on a not good team like the Twins. And Doyle made it only halfway through spring training with the Twins before he was offered back to the White Sox for $25,000 (or half the amount the Twins paid to draft him from the White Sox).
Doyle pitched well in last year's Arizona Fall League but it was more superficially impressive than fundamentally impressive. He did have a 1.98 ERA over 27.1 IP while striking out 22 and walking 5 batters.However, he gave up just 12 hits. You're probably thinking "Isn't it a good thing to not give up hits?" And of course it is. But when you see 12 hits over 27.1 IP - in the notoriously favorable hitting environment of the AFL, no less - alarm bells should be going off in your head. That's a .127 BABIP. Which is ridiculous and totally unsustainable even if your name is 2000 Pedro Martinez.
And Doyle's spring training certainly supported that. He gave up 14 hits in just 5.1 IP (over 3 starts). He walked 3 and struck out just 2 batters. He gave up 10 runs to run his ERA up to 16.88. In short, he pretty much did what you would expect a player of Doyle's ability and experience to do.
Doyle is a fine enough pitcher and he may develop into a useful piece for the White Sox in 2013 or later. But he had essentially no chance to make a major league roster in 2012 and this vindicates the club's decision to leave him off the 40 man roster.
Doyle will be headed to Charlotte.