Shockingly (), John Gibbons is probably the worst challenger in MLB. League average for challenges has been about 50/50 over the last 3 years. Gibbons has been 33% over-turned/67% not over-turned, 42/58, 36/64
https://baseballsavant.mlb.com/replay?challenge_type=&year=2016&challenger=teamchallenging&team=Blue Jays
Gibbons has challenged 155 times over the last 3 years compared to 97 for Buck Showalter.
Other team's fans seem to think that Buck complains a lot but that doesn't hold up through these numbers. Buck is one of the most infrequent challengers in the league, but he's been good at it, getting 53/97 correct.