The Pittsburgh Pirates go after a fifth straight win this evening when they open a three-game set with the San Francisco Giants at PNC Park.

The Pirates continued their recent surge on Thursday, as Jeff Karstens pitched eight shutout innings and Pittsburgh completed a four-game sweep of the Houston Astros with a 2-0 victory.

Karstens (2-2) allowed four hits, walked one and had a season-high eight strikeouts. The right-hander, who was making just his sixth start of 2012 due to being on the disabled list, retired the last eight hitters he faced.

"It was location, command, changing speeds and staying off the middle of the plate. He was very efficient," Pirates manager Clint Hurdle said.

Joel Hanrahan walked Jed Lowrie to start the ninth, but Scott Moore grounded into a double play. After J.D. Martinez walked and went to third on a wild pitch, Hanrahan retired Chris Johnson on a fly ball to right to nail down his 22nd save of the season.

Casey McGehee doubled in a run in the second inning. Karstens singled to start the third and scored on a Garrett Jones sacrifice fly, as the NL Central leaders posted their eighth victory in nine contests.

The Bucs are 10 games over .500 (46-36). Pittsburgh, of course, hasn't had a winning season since 1992.

"We don't have to sneak up on anybody any more, but we have work to do," Hurdle added. "We've worked hard to get to this spot. We're making our way."

A big reason why the Pirates have been so good lately is All-Star outfielder Andrew McCutchen, who is hitting .525 with four homers and 14 RBI in his last 11 home games. He had been 14-for-21 with 11 runs scored before going hitless in three at bats on Thursday.

McCutchen leads the NL in hitting at .365 and is batting a major league-best .444 against left-handers this season. As a team the Pirates are 10-2 at home this year versus southpaws.

That could spell bad news for San Francisco lefty Barry Zito, who takes the hill tonight following losses in four of his last five starts. Zito struggled with his command on Saturday against Cincinnati, as he allowed a run and five hits in six innings. However, he walked six batters and fell to 6-6 on the year to go along with a 3.84 ERA.

Still, Zito has given up just one earned run in his last 13 innings.

"It was a good effort," Giants manager Bruce Bochy said afterward. "He got off a couple innings there and battled himself. He threw six innings and gave up one run -- that's a great job."

Zito has faced the Pirates six times and is 1-3 against them with a 3.25 ERA.

Pittsburgh, meanwhile, will rely on a lefty of their own in Erik Bedard, who is 4-9 with a 4.57 ERA. Bedard lost his second straight start and third consecutive decision on Sunday in St. Louis, as he surrendered five runs and eight hits in only 4 2/3 innings.

Bedard did not get a decision in his only other start against the Giants back in 2004.

He will be trying to add to the misery of a Giants team that comes into tonight's tilt after a three-game sweep at the hands of the Washington Nationals.

San Francisco, which now trails the Los Angeles Dodgers by 1 1/2 games in the NL West, blew a ninth-inning lead on Thursday before falling, 6-5.

The Giants took two of three from the Pirates earlier in the year.