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(SportsNetwork.com) - The San Francisco Giants will try to avoid losing more ground in the NL West when they open a three-game series with the Pittsburgh Pirates Monday at AT&T Park.

The Giants' four-game losing streak has them 1 1/2 games behind the Los Angeles Dodgers for the division lead. The Dodgers just swept the Giants in three games to take over the NL West and recorded a 4-3 win Sunday night.

Hanley Ramirez and Carl Crawford both knocked in runs during a three-run fifth inning and Jake Peavy was dealt the loss in his San Francisco debut. Acquired in a recent trade from Boston, Peavy was reached for four runs -- three earned -- and six hits in six innings. He struck out five and walked two.

Buster Posey homered, while Hunter Pence and Brandon Crawford had an RBI apiece for the Giants, losers in five of the last eight games. The last time the Giants were swept by LA at home was from July 27-29, 2012.

"It's going to be important that we put this behind us," Giants manager Bruce Bochy said on the Giants' website. "We have a tough team (Pittsburgh) coming in here. We have to regroup. You have no choice in this game."

Bochy's club has a good chance at bouncing back with Madison Bumgarner set to take the mound Monday. Bumgarner has won three straight starts and tossed eight scoreless innings in last Wednesday's 3-1 win at Philadelphia.

Bumgarner is 12-7 overall with a 3.19 earned run average and is trying to become the second 13-game winner in the majors (Adam Wainwright, 13).

The left-hander is 4-5 in 10 home starts and 1-2 with a 1.71 ERA in three career starts against the Pirates.

Pittsburgh hopes to slow down Bumgarner and stay in the hunt for the NL Central lead, as it sits three games behind Milwaukee. St. Louis is two games off the Brewers' pace for the division lead.

The Pirates salvaged the finale of a three-game series against the Colorado Rockies with Sunday's 7-5 win at Coors Field. Josh Harrison and Gregory Polanco broke a 5-5 tie with back-to-back home runs in the top of the eighth inning and Travis Snider added a two-run shot early on.

"You're not going to get much of a bigger day from Harrison than what you got today," Pirates manager Clint Hurdle said.

Harrison ended with four hits and Chris Stewart went 3-for-4 with two runs scored for the Pirates, who have won eight of the last 13 games. Tony Watson picked up the win in two innings of relief and Mark Melancon struck out two in the ninth for his 19th save.

The Pirates will also visit Arizona for four games in this road trip.

Vance Worley gets the nod for the Buccos Monday and is 3-1 with a 3.10 earned run average. Worley last toed the rubber in a 12-7 win over Los Angeles last Tuesday and gave up four runs -- one earned -- in six innings.

Worley has made three career starts against the Giants, going 2-1 with a 4.09 earned run average.

Pittsburgh took two of three games at home versus San Francisco back in early May and won the 2013 series with the Giants, 4-3.