The Denver Post looked at the percentage of calls overturned of the MLB's 99 umpires in 2015. Of the more than 1,300 plays reviewed this year, 643 (49.2%) were overturned.
Of the 75 umpires who had ten or more calls reviewed, 43 umpires (57.3%) had worse-than-average overturn rates. Second-year MLB umpire Ben May fared the worst of all: 12 of his 13 reviewed calls were overturned.
Of the 43 umpires with worse-than-average overturn rates, ten are umpiring on the field so far in the 2015 MLB playoffs – that's ten out of a total of 36 umpires assigned post-season duty for the wild card and the division series rounds.