On an 0-2 count, with one out, Astros reliever Hector Ambriz got Phillips to start a swing at a breaking ball. Fletcher ruled that Phillips didn't stop in time.
Phillips turned to Fletcher and pointed to first-base umpire Rob Drake, whom Fletcher could have asked for help, but Fletcher ejected Phillips after listening to him for only a few seconds.
Manager Dusty Baker came out of the dugout and tried to pull Phillips away as he continued to argue with Fletcher.
Wilson Valdez took over at second base in the bottom of the eighth, and committed the error that allowed the game-winning run to score.
Baker said Phillips, who wasn't available after the game, wanted Fletcher to look to Drake for the call.
"Yeah, and then you say a couple magic words, and that's it," Baker said. "He had a rough night on some questionable calls. Sometimes you hit your boiling point. He came in after the game. He felt terrible about it. You don't like it but they happen. These guys are really into these games. There's going to be emotion. We just have to put this one behind us now."
Phillips, who'd entered the game with a 10-game hitting streak, finished 0-for-4 with two strikeouts. He is the third Reds player to be ejected this season, following Devin Mesoraco and Miguel Cairo.
After the game, Phillips tweeted: "#RealTalk... Apologize to my fans, team, & also the umpires for actions tonight! Not like me, but that's how I felt at the time!!!! #Human".
Clark Goble is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.