"Prince just missed four homers. He almost had a four-homer day," Brewers manager Ned Yost said. "You add up his outs, and ... it could have been 1,500 feet."
Fielder singled down the right-field line and was thrown out by Elijah Dukes trying to stretch the hit into a double and then flied out deep three times, including an eighth-inning sacrifice fly that put the Brewers ahead 3-2.
Fielder led off the 11th with an opposite-field double to left against an exaggerated shift and then advanced on Corey Hart's sacrifice. After Russell Branyan struck out, Kapler lined the first pitch from Saul Rivera (3-2) to center for an RBI single.
"Every guy has a different philosophy in regards to pinch-hitting, but mine is just to try to get a good pitch to hit and put a good swing on it -- whether it be early in the count or late in the count," Kapler said.
Milwaukee's Ben Sheets gave up two runs and seven hits in six innings.
Washington managed only one hit in the last five innings: Dmitri Young's disputed two-out solo homer in the eighth.
"When our offense shows up, things will obviously will be easier for us," Nationals manager Manny Acta said.
Young's drive off Brian Shouse was originally ruled in play by second base umpire Paul Emmel. The ball appeared to hit off the top of a wall behind the center-field fence and bounced away from center fielder Mike Cameron for a triple.
Acta asked umpires to confer, and Young was awarded his first homer since Aug. 27 at Los Angeles. As Young trotted home with the tying run, Yost argued to no avail.
"When it bounced, it was too far away," Acta said. "When he hits it, the padding, it doesn't bounce that far away."
Cameron suggested changing the color of the second wall -- which is several feet behind the first -- to alleviate the confusion. Both walls are green.
"They got it right," Cameron said. "They've got to change it or do something to fix that."
Milwaukee split the four-game holiday weekend series, finishing a 4-6 trip.
"It was good to battle back and win this game," Yost said.
Nationals starter Jason Bergmann pitched 5 2/3 scoreless innings, stretching his shutout streak to 19 2/3 innings since being recalled from Triple-A Columbus on May 14. He allowed four hits, struck out eight and walked one, leaving with a 2-0 lead.
"I tried my best for as long as I could," he said. "Hopefully, next time we'll get the W."
Jason Kendall cut the lead with a a run-scoring single off Brian Sanches in the seventh. Young then couldn't backhand pinch-hitter Joe Dillon's check-swing bouncer between first and second, and the ball dribbled into right field for an error that allowed J.J. Hardy to score the tying run.
For the first time this season, Kendall hit eighth instead of ninth. Yost had been hitting Kendall, his catcher, ninth behind the pitcher, in an effort to create scoring chances and avoid double plays. ... The Brewers are close to signing right-hander Julian Tavarez, who was cut loose by Boston two weeks ago. Tavarez will accompany the team back to Milwaukee for a physical Monday night. If he passes, Tavarez could be added to the roster as soon as Tuesday. ... The Nationals are 1-9 in extra-inning games dating to July 27 last year. ... Washington third baseman Ryan Zimmerman was unavailable because of a sore left shoulder. He is day-to-day.