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WASHINGTON -- Carlos Gonzalez has even amazed himself with his sudden power surge.

Gonzalez lead off the eighth inning with a home run for the second night in a row, giving the Rockies the decisive run in a 5-4 win against the Washington Nationals on Wednesday night.

Gonzalez has homered in four straight games and six of the last eight. Before this stretch, he had six homers in 130 career games. His latest landed above the Nationals' out-of-town scoreboard in right field to lead off the eighth inning.

"Yeah, I knew that ball was going to go out," Gonzalez said. "It was a tough pitch. I saw the replay and it was down and away. I was pretty impressed with myself because the pitcher probably did not even know how I hit that ball. It just happened."

The home run gave Colorado a boost after leaving the bases loaded three times in the first six innings.

"We did not do a good job tonight from the standpoint of our situational hitting," Rockies manager Jim Tracy said. "We left the 1st Battalion stranded out there on the bases."

Even though the Rockies stumbled at times, they kept their NL wild-card lead and improved to a season-high 14 games over .500 with a 67-53 record.

Colorado starter Jason Marquis (14-8) gave up nine hits and three runs over six innings, with one walk and one strikeout.

Gonzalez's home run gave the Rockies a 5-3 lead for closer Huston Street, who came on for his 31st save in 32 attempts. He has now converted a team-record 23 save chances in a row, but his last two have not been easy.

Street gave up three hits Tuesday against the Nationals, and gave up a home run to Josh Bard on his first pitch Wednesday night.

"Sometimes you're going to have to win without your best stuff, and that goes from the pitching end to the hitting end to the fielding end," Marquis said. "Tonight was one of those nights. We escaped with the win, and that's all you can ask for."

The Rockies looked as if they had a chance to take a big lead right from the start as Collin Balester (1-3) struggled with his control.

In his previous 20 career starts, Balester had walked more than three batters only once. Wednesday, he walked the first three batters, and four of the first five. He added an error, throwing an attempted pickoff into center field.

After Balester walked the bases loaded, Troy Tulowitzki hit a two-run double down the left-field line. Brad Hawpe followed with a walk. When Balester got No. 6 hitter Ian Stewart to fly out to left for the first out, the crowd responded with a loud sarcastic cheer.

Balester got out of the inning, but was back in trouble in the second. Marquis led off the inning with a double, and scored on Dexter Fowler's triple. Balester's night ended with a walk to Todd Helton, the fifth he issued. The 1 1/3 innings were the shortest outing of Balester's career.

Balester said his control problems came from working too quickly and speeding up his delivery -- a tendency he's been aware of.

"I've pinpointed it, and now I now need to execute it," Balester said. "I've been trying so hard, and I think that's my biggest problem. I've been trying too much."

Saul Rivera came on to get the last two outs of the inning as the Rockies left the bases loaded for the second time.

Barmes hit his 20th home run of the season in the fifth inning off Rivera to give Colorado a 4-1 lead.

Washington rallied in the fifth. Nyjer Morgan tripled, Cristian Guzman drove him home with a single and Ryan Zimmerman followed with an RBI double, all with two outs. Zimmerman also drove in the Nationals' first run of the night with a triple in the first inning.

Gonzalez's solo home runs have given the Rockies a lift in a pair of one-run wins to start the series against Washington. Now Tracy has one more request for his left fielder.

"You would like to see one of those every once in a while with the bases loaded, but I won't beg," Tracy said.

Game notes

Nationals RHP Jordan Zimmermann had reconstructive elbow surgery Wednesday morning in California and will travel back to Washington Thursday. He is expected to be out 12 to 18 months. ... Colorado has an eight-game winning streak against the Nationals. ... The Nationals sold 6,000 tickets for $1 apiece for Friday's game in 3 hours Wednesday, part of a promotion tied to an on-field, pregame news conference with newly signed No. 1 draft pick Stephen Strasburg.