PITTSBURGH -- Charlie Morton gained the nickname "Ground Chuck" in recent years for his propensity to get ground balls with his sinking fastball.

However, "Uncle Charlie" might have been a better moniker for the Pittsburgh Pirates right-hander Tuesday night with the way he tied up the San Francisco Giants with his curveball.

Morton pitched into the seventh inning, second baseman Neil Walker hit a two-run home run and the Pirates blanked the Giants 4-0 on Thursday night.

Morton (8-4) scattered four hits over 6 2/3 innings while striking out eight and walking two. The right-hander was pulled in the seventh inning with a four-run lead after the Giants loaded the bases with two outs.

Right-hander Jared Hughes, who got center fielder Gregor Blanco to line out to end the seventh-inning threat, and left-hander Tony Watson completed the six-hit shutout.

"We're watching Charlie develop into more of a complete pitcher instead of a pitcher with a good sinkerball," Pirates manager Clint Hurdle said. "His curveball was really good. We saw it at times last year when the pitch started to develop for him. It has so much tilt and depth on it, and there's enough fastball that you can't sit on the curve. It makes it a challenge to square him up."

Morton honed his curve to give him a pitch to get out left-handed hitters.

"Lefties have taken the lower third of the strike zone away from me because they've been looking for the sinker and having success against it," Morton said. "It's been a bit of evolution but you always need to evolve as a pitcher, as a person."

Walker, the switch-hitting second baseman, hit his 13th home run of the season in the sixth inning off right-handed starter Jake Peavy (3-6) to push the Pirates' lead to 4-0.

However, Walker was more impressed with Morton than his homer.

"It's fun to play behind him when he's going well because he gets a lot of ground balls that lead to a lot of quick innings and you get on and off the field in a hurry," Walker said. "He was really good tonight."

Pittsburgh had gone ahead 2-0 on two-out RBI doubles by third baseman Aramis Ramirez in the first and shortstop Jung Ho Kang in the third.

Walker, Kang and left fielder Starling Marte, who extended his hitting streak to five games, each had two hits. Marte is 9-for-23 (.381) during his streak.

The Pirates (72-45) moved a season-high 25 games over .500 with their seventh win in eight games, pulling within 4 1/2 games of the idle St. Louis Cardinals in the National League Central.

Pittsburgh also won 33 of its last 43 games at home and is 42-19 at PNC Park this season. The Pirates also improved their season record against NL West teams to 17-3, including 4-0 against San Francisco.

"We're playing really well right now and it's a situation where everyone is contributing, one through 25 on the roster," Hurdle said.

The Giants (65-56) dropped 2 1/2 games behind the Los Angeles Dodgers, who were off, in the NL West.

Peavy allowed four runs and seven hits in six innings with five strikeouts and one walk. He won all three of his career starts at PNC Park but was pitching in Pittsburgh for the first time since 2008.

"I thought he settled down," Giants manager Bruce Bochy said. "He was throwing the ball well. It was a 2-0 ballgame going into the sixth. That's not bad.

"We just couldn't generate any offense. Their guy was just really good. He had movement on his fastball and a good curveball. We just couldn't get much going."

Giants shortstop Brandon Crawford's career-best 13-game hitting streak ended as he went 0-for-3 and was hit by a pitch.

NOTES: The Giants acquired OF Marlon Byrd from the Cincinnati Reds in a trade for a minor leaguer before the game and he is expected to join the team Friday. Byrd will play right in place of RF Hunter Pence, who was put on the 15-day disabled list Thursday with a strained left oblique muscle. ... San Francisco LF Nori Aoki was activated from the seven-day concussion DL after having been out since Aug. 13 and went 1-for-3 with a stolen base. ... Pirates 3B Josh Harrison (torn left wrist ligament) and SS Jordy Mercer (sprained left knee) could both be activated from the DL before the four-game series ends Sunday night. Harrison has been out since July 6 and Mercer went on the DL on July 20. ... 1B/OF Corey Hart (left shoulder impingement/right knee discomfort) joined Triple-A Indianapolis for a rehab assignment that will likely run through the end of the month. ... The second game of the series is Friday night, with San Francisco LHP Madison Bumgarner (14-6, 2.98 ERA) facing Pittsburgh LHP Jeff Locke (6-7, 4.31 ERA).