If the Arizona Diamondbacks were counting on duplicating last season's second-half run, they're not off to a very good start.

Darwin Barney homered and Matt Garza threw seven shutout innings to lift the Chicago Cubs over the Diamondbacks 3-1 on Sunday.

Barney clubbed a Trevor Cahill pitch into the left-field bleachers for a two-run homer in the second inning to help complete a three-game weekend sweep of Arizona.

"We expect ourselves to be better," Diamondbacks first baseman Paul Goldschmidt said. "We're not going to win a ton of games scoring one run."

The defending NL West champion Diamondbacks had the second-best record in the National League after the All-Star break last season, but they opened the second half this year by getting swept for the first time at Wrigley Field since May 2008.

Chicago outscored Arizona 15-3 in the series.

"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."

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

"Seems like this year, when I walk a guy they score, so I kind of attack the zone," Cahill said. "Just can't find it."

Aaron Hill hit his 12th homer in the eighth and reached base three times to pace the struggling Arizona offense. His homer snapped a 14-inning scoreless streak for Cubs reliever Shawn Camp.

"We just haven't been able to put anything together," Goldschmidt said. "It's hard when you're struggling. It's not one thing or one guy specifically. Hopefully tomorrow we'll come out and score a bunch of runs."

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.

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.

"Parra hits a bullet right at Marmol, that's the frustrating part about it is those guys keep battling," Gibson said. "It's frustrating, their busting their tales, but that's what baseball does to you."

Barney's homer was his fourth of the season, doubling his total from 2011.

"It was a slider, a chase pitch and it backed up inner half," Cahill said. "Usually you don't want to throw a slider on the inside part of the plate to a right-handed hitter."

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

Garza struck out Justin Uptown 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.

Upton, the subject of trade rumors himself, went 0 for 4 and went hitless in 10 at-bats during the series.

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. He pinch-hit in Saturday's contest and Diamondbacks manager Kirk Gibson said the club is hoping to avoid placing Kubel on the disabled list. ... Cahill, who entered the game with just three hits in 45 at-bats, singled twice for his first career two-hit game.