WASHINGTON -- The double switch on defense does not normally lead to an offensive surge.

But that is what happened on Sunday for the Colorado Rockies and manager Walt Weiss, whose last-place club had won just 20 road games coming into a three-game weekend series in Washington.

DJ LeMahieu, who entered the game to play second base in the seventh inning on a double switch, had a two-run single with two outs in the eighth to break a 4-4 tie as the Rockies beat the Nationals 6-4.

"It's huge. We have had a lot of clutch performers and DJ was one of them," Weiss said. "A lot of big-time performances. We have lost some of those" close games this year.

The game-winning hit came against Drew Storen (2-2), the former closer who also blew a three-run lead in the eighth inning Friday and then gave up two runs in the eighth Sunday.

"He's a closer pitching the eighth inning. We all know that," Weiss said of Storen, who lost his closer role when the Nationals traded for Jonathan Papelbon in late July. Late-inning pitchers "are not perfect."

Tommy Kahnle pitched the ninth for the Rockies and recorded his second save of the series as he got shortstop Ian Desmond on a grounder for the final out with the bases loaded. Kahnle once again used his changeup as he got his second career save after no saves in the first 84 appearances of his big league career.

"He is comfortable with his changeup. He can get swings and misses," Weiss said of fellow New York native Kahnle, a product of Division II Lynn University.

Carlos Gonzalez, the Rockies right fielder, hit two solo homers to give him three in the series and 25 on the year. Gonzalez hit a grand slam off Storen in Friday's comeback win.

The winning pitcher Sunday was John Axford (4-5), who came on in the seventh and pitched 1 2/3 innings of scoreless ball.

Washington first baseman Ryan Zimmerman had three hits and also smashed two solo homers, but the Nationals remained 1 1/2 games back of the first-place New York Mets in National League East.

"I think it is important for us to realize where Drew has been" and his past contributions, Washington manager Matt Williams said.

Said Storen: "I made some good pitches and some groundballs found a hole."

Colorado (47-62) won two of three games in the series and is 13-8 against the National League East. Second-place Washington (57-53) ended the homestand 3-4 and has lost seven of its last 10 before starting a three-city road trip that begins Monday in Los Angeles.

The Nationals had tied the game at 4-4 in the sixth when left fielder Jayson Werth scored on a fielder's choice off the bat of center fielder Michael A. Taylor. The ball was fielded by Gold Glove third baseman Nelson Arenado but his throw home hit Werth and allowed him to score.

Gonzalez hit his second solo shot of the game in the sixth off Washington starter Max Scherzer to tie the game at 3-3. It was the fourth multi-homer game this year for Gonzalez and the 14th of his career.

"You have to be aggressive in the zone," Scherzer said of facing Gonzalez. "Guys took good swings against me. It was one of those games where you can't beat yourself up."

Later in the inning, left fielder Kyle Parker, following a two-out intentional walk, ripped an RBI single to give the Rockies a 4-3 lead.

The Rockies cut the lead to 3-2 with a solo homer in the fourth by second baseman Daniel Descalso.

Washington grabbed a 3-1 edge in the third on Zimmerman's second solo homer of the game off starter Yohan Flande.

The Nationals had taken a 2-1 lead in the second on back-to-back homers by Zimmerman and Werth.

Colorado had grabbed a 1-0 lead in the first when Gonzalez hit his first homer.

Scherzer gave up four runs and eight hits, including three homers, in six innings but was not involved in the decision. The first six runs of the game came on solo homers.

Flande allowed six hits and also gave up three homers. He yielded three runs in 4 2/3 innings but also did not factor in the decision.

First baseman Ben Paulsen also had two hits for the Rockies.

"There is no reason we can't win. It leaves a sour taste in your mouth," Scherzer said of the series loss.

NOTES: Washington will begin a three-city road trip on Monday against the Dodgers in Los Angeles with LHP Gio Gonzalez (8-4, 3.75 ERA) going for the Nationals against Dodgers LHP Brett Anderson (6-6, 3.06 ERA). ... Colorado RHP Jon Gray (0-0, 4.50 ERA) will start on Monday in New York against Mets LHP Jonathan Niese (6-9, 3.51 ERA). ... Colorado CF Charlie Blackmon, who had two doubles off Stephen Strasburg on Saturday, entered play Sunday as the National League leader among leadoff men in RBIs (46) and extra-base hits (42). ... Washington RF Bryce Harper reached base in 34 of his previous 35 games before Sunday, and led the majors in hitting (.337), slugging (.663) and on-base average (.466). He got on base again Sunday, going 1-for-5, but his batting average dropped to .335. ... The Nationals voided the option of RHP Aaron Barrett and placed him on the 15-day disabled list with a right elbow sprain, retroactive to Thursday. Barrett had been optioned to Triple-A Syracuse on Thursday. He is 3-3 with a 4.60 ERA in 40 games out of the bullpen for Washington.