His whole bullpen management yesterday was suspect. Schmidt is stretched out so it didn't make sense to only let him throw 45 pitches, especially if he knew he couldn't go to any of his best arms in the pen. That was his first mistake, pulling him too early. Then after that he pulled Peralta after 3 batters even though he looked great (2 Ks and someone reaching on a blown call at first) and was only at 13 pitches. Did he bring Weissert in for the righty on righty matchup? Well Peralta has a great changeup that neutralizes righties (RHB hitting .234/.304/.290 against him this season) so that wouldn't make sense. Weissert has had some good moments but is still an unreliable rookie, and there's not really any excuse for bringing him in to face the Twins' best hitter.
In general I feel like most wins/losses are the result of players and not coaches, but yesterday's loss was definitely on Boone.