A look at the history and concerns over the split-finger fastball and whether or not we should apply those concerns to Junior Guerra. Also, look who has arguably the best splitter in baseball!
The split-finger fastball and the MLB have had a messy breakup.
They say the splitter was in vogue during the 1980's (I wasn't around for the 80's, nor is there any PITCHf/x data available from that time period to sort through, so I have to go entirely off of hearsay). Almost every pitcher threw one, as they recognized its innate ability to create swings-and-misses.