The Colorado Rockies entered the season with World Series aspirations. A weak end to their weekends has pretty much dashed those hopes.

The Rockies have lost 16 straight Sunday games, a slump that now includes their 3-2 defeat by the Washington Nationals.

"This isn't the first time on a Sunday that we played like this," manager Jim Tracy said. "The game was sitting right there for the taking. We did not capitalize and do enough execution what we needed to get done to win this game."

After starting the year 2-0 on Sundays, Colorado has been winless.

The Rockies spotted the Nationals a 2-0 lead when Jonny Gomes hit his first home run for Washington. They rallied to tie it in the seventh but Jayson Werth delivered a tiebreaking single in the eighth inning to continue Colorado's Sunday woes.

The Rockies split the four-game series and went 2-5 on their homestand. Eliezer Alfonzo got three hits for Colorado and Troy Tulowitzki had two.

Rockies starter Aaron Cook, who had to leave Tuesday's game against Philadelphia because of neck spasms, scattered four hits in 6 2-3 innings. He walked three and struck out three in his second longest outing in his 10 starts since coming off the disabled list on June 8.

"I felt pretty good. There was a little mechanical issue early and left one ball up. Ended up costing us big," he said. "Other than that I felt pretty good and felt I was able to make pitches the way I needed to."

Washington scored the deciding run off reliever Matt Belisle (5-4). Danny Espinosa opened the eighth with a double over Young's head in left and moved to third on Ryan Zimmerman's groundout. After an intentional walk to Michael Morse, Werth singled sharply to left field.

Young took a poor angle on Espinosa's double, opening the door for the Nationals.

"Unfortunately we had a tough defensive play when they scored the go-ahead run in the top of the eighth," Tracy said. "That's a catchable ball. But we didn't catch it."

Tyler Clippard (2-0) got the win in relief and Drew Storen pitched the ninth for his 29th save.

The Nationals scored in the second when Werth led off with a walk and Gomes followed with his 12th home run. He had gone 25 games without a homer, a drought that started before the Nationals acquired him from Cincinnati on July 26.

The Rockies tied it in the seventh. Pinch-hitter Jonathan Herrera drew a leadoff walk from starter John Lannan, Eric Young Jr. singled off reliever Ryan Mattheus and Dexter Fowler's sacrifice bunt moved the runners up.

Herrera scored when Morse bobbled Carlos Gonzalez's grounder at first, and Gonzalez was safe when Clippard failed to cover the bag. After Tulowitzki struck out, Ty Wigginton singled to make it 2-all.

The Rockies had a chance to tie it in the eighth when Mark Ellis reached on a fielder's choice and stole second but Herrera flew out and Young grounded out.

The Rockies stranded 11 runners.

"We had opportunities offensively. We had the bases loaded and one out in the fourth inning and didn't score," Tracy said. "We tied the game with two outs and had a chance to take the lead, but popped the ball up. And we had an opportunity in the eighth inning."

NOTES: The Rockies recalled RHP Josh Roenicke from Triple-A Colorado Springs and optioned RHP Greg Reynolds to the Sky Sox. ... Chien-Ming Wang will pitch in Washington's opener against the Cubs in Chicago on Monday. Wang has not faced the Cubs since June 18, 2005, and has never pitched in Wrigley Field. ... Rockies starter Jason Hammel will open Colorado's series in Cincinnati on Monday. Hammel has struggled since starting the season 3-1, going 3-10 since then. In July opponents hit .325 off the right-hander. ... Tulowitzki has at least two hits in four straight games. He was 10 for 16 in the four-game series.