Showalter and Reynolds were ejected after a call on the Tigers' Jhonny Peralta was reversed, with Reynolds' foot ruled off the bag after first-base umpire Jeff Kellogg originally called Peralta out.
"I've never in my life seen someone reverse a call," said Reynolds, who was tossed by second-umpire Vic Carapazza after spiking his glove. "This game is way too important right now, where we are in the season, for these kinds of calls to happen. And it's very frustrating."
Added Showalter: "That's a new one on me. They're trying to get it right, but they didn't.
"I was shocked, especially with as good a play that Mark had made. Manny [Machado] made a great play on it, too."
Showalter also questioned a call in the first inning, when Nick Markakis was ruled out on a play at the plate.
The Peralta play was officially scored as an error on Machado -- who made a great backhanded stop just to get to the ball -- and although Hunter got out of that unscathed, he wasn't as lucky in the sixth, when Fielder sent the first pitch he saw into the right-field concourse for a game-tying two-run homer that went an estimated 462 feet.
Two innings later, Fielder's game-winning homer came off lefty reliever J.C. Romero, who replaced Darren O'Day after O'Day's two-out walk had put Miguel Cabrera onboard. Romero got ahead, 1-2, then went with an inside fastball that Fielder looked like he was waiting on.
"Sometimes you have to tip your hat to the hitter," catcher Matt Wieters said of Fielder's bomb. "He hit a pitch that was off the plate and in. The impressive thing about it was it started on the foul pole and was able to get fair. As hitters, it's impressive to be able to pull your hands in enough to keep that ball fair. ... The wind might have helped bring it back a little bit."
Wieters -- who took Detroit starter Justin Verlander to the warning track in his first at-bat -- sent a full-count offering into the right-field stands for a two-run homer in the fifth inning. The blast, his 17th of the season, also scored J.J. Hardy and gave the O's a two-run lead. Baltimore, using four walks, was able to chase Verlander after just six innings.
"It's a tough one for us, but if I know our guys and what we've been doing all year, they're going to bounce back," Showalter said of his team's third loss in 13 games. "There's not much explanation. The one [call] that really ticked me off was throwing Reynolds out of the game for throwing his glove down. That's an equipment fine."
"He had no right to throw me out there," Reynolds said. "There's just so many words I can't say.
"There's got to be some kind of replay for this. It's to the point where all these calls that get missed cost people runs, cost people outs. Cost [Hunter] extra pitches. I can't say how I really feel, but it's pretty obvious."