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LOS ANGELES -- Andre Ethier and the Los Angeles Dodgers are making a habit of fantastic finishes.

Ethier's two-run homer in the 13th gave the Dodgers a 4-2 victory over the Colorado Rockies on Monday night in the opener of a suddenly significant series between NL West teams.

It was Ethier's fourth walk-off hit this season and the 14th time the Dodgers have won in their final at-bat. They improved the best record in the majors to 49-28.

"I can't believe we did it again," said Ethier, who hit three home runs last Friday against Seattle. "I'm just enjoying it and having fun."

The Dodgers left the potential go-ahead run in scoring position five times in a span of six innings starting with the seventh. Juan Pierre stole a base in three different innings during that stretch, but they couldn't cash in until Ethier came through with the team's ninth walk-off hit of the season.

"It was a taxing night," manager Joe Torre said. "Juan Pierre tried to do it himself. He was just trying to will himself around the bases. We had some ugly swings out there, but you have to give them credit. Their bullpen was as good as our bullpen."

Rockies closer Huston Street wasn't available to pitch, having saved all three victories at Oakland last weekend, so manager Jim Tracy had to scramble for the right combination out of the bullpen.

Joel Peralta, the sixth Colorado pitcher, began his third inning of work by giving up a single to Casey Blake in the 13th. The next batter was Ethier, who drove the right-hander's 39th pitch to right field on a 1-2 count for his team-high 15th homer and 14th at home.

"Knowing that Huston was down and that they were trying to stay away from him, I just tried to go as long as I could to give the team a chance to win the ballgame," Peralta said. "It's not something I haven't done before. When I came out after my second inning, they asked me how I felt and I told them I felt good."

Peralta (0-1) had made 11 straight scoreless appearances since May 25 against the Dodgers at Coors Field, when he gave up an RBI single to Russell Martin.

"To me, it was the perfect pitch to throw in that situation, because normally I get ground balls or a swing and a miss with it -- like I did the first two innings," Peralta said. "The pitch was supposed to be better than that, a little bit lower. But it was right in the middle of the plate, he got out in front of it and put a good swing on it."

James McDonald (2-1), the eighth Dodgers pitcher, struck out two in a perfect inning for the win. Los Angeles improved to 9-1 against Colorado this season. The Rockies remained the only team in the majors without an extra-inning victory, dropping to 0-4.

The Dodgers had a 14-game lead over Colorado at one point, but it had shrunk to 7½ going into Monday night thanks to a 20-3 Rockies surge.

Jeff Weaver came on in the 10th for the Dodgers, and Ryan Spilborghs -- who homered earlier against Randy Wolf -- greeted him with a leadoff double before advancing to third on Chris Iannetta's single to left. But the right-hander struck out the next three batters, including Dexter Fowler and Clint Barmes with runners at second and third.

The Dodgers, coming off consecutive losses to Seattle in their final interleague series, are the only team in the majors that hasn't lost three a row. The last time that happened was Aug. 29, when they dropped their eighth straight before winning the next eight.

Wolf gave up two runs and four hits over six innings, including Spilborghs' sixth homer and first since June 4. The left-hander has allowed 15 home runs in 102 1/3 innings.

Wolf tied it at 2 with a two-out, two-run single in the fifth after a balk by Rockies starter Ubaldo Jimenez advanced two runners.

Jimenez yielded five hits over seven innings. The right-hander lost his previous three starts against the Dodgers this season, allowing 17 earned runs, 24 hits and 10 walks in 15 innings, after going 4-0 in his first six starts against them. His lifetime ERA against Los Angeles is 6.31.

Game notes

Dodgers closer Jonathan Broxton, pitching for the first time in six days, struck out the side in the ninth. ... Wolf's no-decision was his 11th in 17 starts this season. ... Wolf is 3 for 30 at the plate with five RBIs. ... Blake turned Garrett Atkins' line drive to third base into an inning-ending double play in the fourth, diving to the bag to tag it just before Fowler could scramble back.