The Brewers were trailing at the time, 6-2, and trying to avoid their second straight loss.
After allowing a one-out single in the fifth inning, Parra walked two straight batters to load the bases, then allowed opposing pitcher Bronson Arroyo to hit a two-run double.
Two batters later, Joey Votto hit a two-run, two-out single past Fielder, who made a diving attempt. According to one player, that play had nothing to do with the argument.
"Walks kill you," said Parra.
Yost downplayed the altercation after the game.
"It's not a big deal," Yost said. "For eight months a year, we're a family, and at times things happen. Tempers flare up. But it's within the family, and it's a little bit rude when your neighbors are fighting next door for you to go over and ask what happened. That's kind of the case here. It's nobody's business what happened."
"It's already taken care of," Parra said. "Nothing needs to be talked about. In the Minor Leagues, there's no cameras on it, [but] stuff like that happens all the time.
"I just want to focus on my next start."
"A lot of guys are getting frustrated," shortstop J.J. Hardy said. "I don't see too many good things that can come of it, but we're all grown men. We'll get over it. It could have gotten a lot worse if we didn't break it up quickly. I was just yelling, 'Relax!'"
Said left fielder Ryan Braun: "If the team were to become divided it can certainly become a negative thing, but this is not one of those issues. ... It's like bickering and fighting with your brothers. You spend so much time with people, not just on the field but off the field, inevitably there's going to be times where you don't agree on things. Sometimes you need that emotion, that passion, to break up the monotony. It's not necessarily a bad thing.
"I'm sure they'll hate each other for a couple of days, get over it and be friends soon enough."
Yost hinted that discipline was in order, but the manager declined to go into detail. Fielder, through a club spokesperson, refused to answer questions about the incident.
"You never want stuff like that to happen," infielder Craig Counsell told the Milwaukee Journal Sentinel. "But who cares? We lost tonight. That's the worst thing that happened.
"It's forgotten when we come here tomorrow. We've got to win the game tomorrow. All your focus is trying to win the game tomorrow. It's not surprising. We're all competing and trying real hard. It's going to happen.
"You know there's not a problem in this clubhouse. You know that. We have tempers. We're humans. There's a bad side to everybody. It happens but we're going to move on."
Adam McCalvy is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.