Bernadina hit his first two major league homers, including a tiebreaking shot off Francisco Rodriguez in the ninth inning, and made a marvelous catch to lead the surprising Washington Nationals past New York 6-4 on Wednesday.
"He had, so far, the game of his career," Mets outfielder Jeff Francoeur said.
Starting pitcher Craig Stammen drove in three early runs with a pair of hits for the Nationals (19-15), who took two of three from New York to win their third straight series -- all against NL East foes.
Coming off consecutive 59-win seasons, second-place Washington improved to 4-2 this year at Citi Field and 6-1-1 in its last eight series overall.
In this one, Bernadina did it all.
"It's good to see him coming into his own," Stammen said.
Tyler Clippard (7-1) worked a hitless inning and leads the majors in wins. He shook off the loss he took Tuesday night when the Nationals squandered a four-run lead in the eighth.
Matt Capps tossed a perfect ninth for his big league-best 14th save in 14 chances, sending what was left of the sparse crowd home on a damp and misty, 48-degree day.
Cristian Guzman singled off Rodriguez (2-1) with one out in the ninth. One out later, Bernadina, known for speed but not power, drove an 0-1 pitch into the Washington bullpen in right-center for his third hit of the game.
"It was his day," Rodriguez said.
New York tied it at 4 by scoring twice in the fifth off Stammen. Angel Pagan doubled, Alex Cora hit a run-scoring single and Jose Reyes lined an RBI double down the right-field line to snap a 9-for-44 slump.
Moments later, the Mets appeared poised to take the lead when Francoeur sliced a bases-loaded drive to deep right. But Bernadina retreated quickly on the slick grass and, with a fully extended dive, robbed Francoeur of an extra-base hit that surely would have scored three.
"I feel more confident and that's why I think things are getting better," Bernadina said.
Francoeur, stuck in a 12-for-84 (.143) slide, slammed his helmet to the ground in frustration after rounding first base.
"That ruined my day," he said. "It's one of those plays that sticks with you until you wake up the next day."
Washington went ahead in the second inning. Adam Dunn hit a leadoff double and went to third on Guzman's single. A walk to Willie Harris loaded the bases with nobody out, but Mike Pelfrey nearly wriggled out of the jam. He struck out Bernadina and Wil Nieves, leaving only the pitcher in his way.
Stammen, however, lined a 2-2 pitch through the left side for a two-run single.
Pelfrey also produced at the plate, hitting an RBI single in the bottom half that preceded Pagan's sacrifice fly.
Bernadina hit a solo shot to right with two outs in the fourth for his first homer in 115 career at-bats.
"The coaches felt he was ready to break out," Nationals manager Jim Riggleman said. "Before the game, I told the coaches I expected him to hit a double and a triple today. It turned out, it was even better."
Nieves followed with a double and Stammen bounced a single up the middle to make it 4-2. It was the eighth major league RBI for Stammen, who owns a .244 career average in 45 at-bats.
"It's usually going to be a long day when the pitcher has three RBIs on the other side," Pelfrey said. "That's unacceptable."
Washington right-hander Jason Marquis is scheduled for surgery Friday to remove bone chips from his ailing right elbow. He is expected back in August, general manager Mike Rizzo said. ... Stammen's three RBIs were the most by a Nationals pitcher since the franchise moved to Washington. Guillermo Mota, pitching in relief, also drove in three runs on June 9, 1999, for the Montreal Expos against Boston. ... Nationals catcher Ivan Rodriguez, batting .383, was rested. ... Pelfrey was pulled after 5 2/3 innings. He threw 119 pitches, matching a career high. It was the most by a Mets pitcher this season. ... Reyes, moved from leadoff to No. 3 in the lineup on April 23, was 7-for-38 (.184) with runners in scoring position before his double drove in Cora from second base. ... Washington is 6-1 in series rubber games this season. The Mets are 0-6.