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CHICAGO -- The starting rotation is on a roll and the question is whether the Chicago Cubs can keep it going.

Matt Garza threw seven shutout innings and Darwin Barney homered to lift the Chicago Cubs to a three-game sweep of the Arizona Diamondbacks with a 3-1 win Sunday.

Garza's outing was his best since late April and continued a five-game stretch during which Chicago's pitchers have posted a 1.23 ERA.

"I felt good today," Garza said. "I was able to stay in my mechanics today, and when I didn't I was able to catch myself and adjust quick."

Barney clubbed a Trevor Cahill pitch into the left-field bleachers for a two-run homer in the second inning to help Chicago match a season high with its fourth straight win.

"It's not my approach but you've got to make adjustments at this level," Barney said. "Two strikes, I'm looking to hit the ball the other way toward second, but luckily I ran into something."

Garza (5-7) held Arizona to five hits and one walk, striking out seven en route to his first win in July. He's allowed three earned runs or fewer in his last 18 starts at Wrigley Field.

"Who knows why certain people pitch better in certain ballparks, pitch better at home than on the road?" Cubs manager Dale Sveum said. "He's been pretty outstanding at home, there's no doubt about it."

Carlos Marmol got the last two outs for his 10th save. He allowed a pair of baserunners, but struck out Geoff Blum and got Gerardo Parra on a comebacker to end it.

Cahill (7-8) allowed three runs on four hits over 5 1/3 innings, losing for the third time in his last four decisions.

Aaron Hill hit his 12th homer in the eighth and reached base three times to pace the struggling Arizona offense.

"When you're not hitting, it magnifies things," Arizona manager Kirk Gibson said. "The story of the series was our lack of offense and inconsistency."

Barney's homer was his fourth of the season, doubling his total from 2011. He reported to spring training this year with a bulkier physique in response to last season, when he wore down.

"Losing 20 pounds last year, that was hard. It's hard on your body," Barney said. "I've done a decent job of maintaining this year. It just gives you more energy."

Barney added a sparkling play up the middle on Parra's grounder to end the Arizona seventh and extended his errorless streak at second base to 75 games.

"Like I said before, there's nobody that's been better at second base than he has," Sveum said.

Rookie Anthony Rizzo singled up the right-field line to score David DeJesus in the first. Rizzo is hitting .356 with 10 RBIs in 15 games since being recalled from Triple-A Iowa.

"When we brought up the kid, it was real exciting," Garza said. "Real exciting. Putting his presence in the lineup, you see what happens."

The streaking Cubs have won 12 of their last 16 games since June 25, the best record in baseball over that span. Chicago outscored Arizona 15-3 in the series. Nevertheless, Chicago has had to deal with rumors about the team being broken up through trades.

"You think about that a lot," Sveum said. "You don't dwell on it, but just to be having a streak like this and win a lot of ballgames, you don't want to lose pieces to that puzzle."

Garza and fellow starter Ryan Dempster in particular have been the subject of ubiquitous trade rumors. With scouts of several teams in attendance Sunday, Garza was in control throughout, allowing more than one baserunner in just two of his seven innings.

Garza said he has a good reason to ignore trade scuttlebutt.

"I've got a wife who is due in about 23 days, so rumor mill can wait," Garza said. "That's the last thing on my mind right now. I've got a wife who is just ready to pop."

Garza struck out Justin Upton swinging with two on to end the third, getting the struggling slugger on an off-speed pitch. He repeated the trick against Parra, who chased a pitch in the dirt with two runners on to end the fourth.

As for the trade rumors, Barney -- another name that has cropped up -- echoed Garza's sentiment that he's content to stay put.

"Being a Cub since I was drafted, you don't like hearing those things," Barney said. "It's nice to know people are interested. But I want to be here. Whatever happens, happens. It's a business."

Game notes

Arizona OF Jason Kubel was held out of the starting lineup for a second straight day because of tightness in his right hamstring. He suffered the injury while slipping on a wet field in Friday's game. ... Former Cubs pitcher Kerry Wood paid a visit to his old clubhouse before the game, his first trip to Wrigley Field since his retirement ceremony on May 19. ... Cahill, who entered the game with just three hits in 45 at-bats, singled twice for his first career two-hit game.