After two innings of duty Saturday, Mota returned in the eighth inning of Sunday's game with the score tied. He breezed through the eighth, but then he opened the ninth by walking Dukes, who is batting .105.
Pinch-hitter Dmitri Young hit a double to take Dukes to third, and Mota then threw a wild pitch that hit in front of batter Felipe Lopez in the dirt, and Dukes took home to score the winning run.
"We tried to go with a changeup, but it got through and there was no chance to get to it," catcher Mike Rivera said, adding that the situation started with the Dukes walk.
"We were one pitch away from getting Elijah," Rivera added.
Despite pitching in his fourth inning over two days, Mota said he was not fatigued.
"I'll pitch anytime they need me," Mota said. "I was out there trying to do my job. I feel strong. That's what I'm here for."
Yost added that the team was low on options, because the batting matchups prevented him from bringing in a left-handed specialist.
"We were looking at [Carlos] Villanueva in the next inning if we were still tied -- seeing if he could pitch a couple innings," Yost said.
It was the third straight game in which the Brewers made a prominent defensive mistake. On Friday, it was shortstop J.J. Hardy who bobbled a ball to start a four-run Nationals rally, and Saturday, third baseman Bill Hall had a pair of miscues in the ninth inning that the team was unable to overcome.
The ending overshadowed a six-run comeback by the Brewers. First, they dug an early hole by allowing a three-run fourth inning. Ryan Zimmerman and Aaron Boone singled, then Lastings Milledge had an RBI double. Wily Mo Pena hit a two-run double to cap off the scoring.
The Nationals struck again in the fifth. Cristian Guzman was walked, and then Aaron Boone hit a 91-mph fastball into the left-field seats for a two-run home run, his fourth of the season.
That also got starting pitcher Manny Parra removed from the game, though the Brewers' comeback gave him a no-decision.
Parra looked mortal again after a pair of strong outings.
"I just have to keep the same mindset I had before," Parra said. "[I have to] be aggressive, keep the ball down. I didn't keep the ball down."
But the sixth inning was rally time for the Brewers, and they finished the inning with six runs.
Prince Fielder opened and closed the inning. In between, one of the highlights included a home run by Corey Hart, his second in two days. Hart fought through a 3-2 count to hit the homer to right-center field on the 10th pitch of his at-bat.
"You're down six, and it shows that your team is still fighting and pushing," Yost said.
Yost said that the team would rally behind Sheets on Monday to try to salvage a series split against the Nationals before heading home. He said he wasn't concerned about Parra, because the young pitcher just made a couple mistakes.
"Once he gets to the point where he can consistently get the ball down, he's going to be a force in this league," Yost said.