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After an immensely satisfying three-game sweep at San Francisco that put the Dodgers in a virtual tie for the NL West lead, manager Don Mattingly was concerned about how much emotion his team had left for the opener of a series against another contender.

During batting practice, Mattingly referred to these three games against the Arizona Diamondbacks as a "trap series," one that presented the danger of the Dodgers coming out flat.

Sure enough, they lost 7-2 Monday night as Paul Goldschmidt hit a three-run homer in the first inning against Aaron Harang, and Chris Johnson added a grand slam in the fifth against the 35-year-old right-hander.

Harang (7-6) gave up a season-high seven runs over five innings, along with nine hits and three walks. He is 1-7 with a 3.26 ERA in his last 12 starts against the Diamondbacks since beating them in consecutive starts with Cincinnati back in August 2003. During that stretch, they have homered off him 10 times.

Harang found himself trailing 3-0 after just eight pitches, as Goldschmidt hit his 14th homer after singles by Gerardo Parra and Aaron Hill.

"I was hitting my spots in the 'pen. Usually that leads to a tough night, a grinding night," Harang said. "Having done this so long, you get a feeling."

"There's times you can get through it with minimal damage. The fact that two pitches were what changed the game was frustrating," he said.

Goldschmidt homer was a fitting send-off for his mentor, veteran first baseman Lyle Overbay, who was designated for assignment in order to clear a spot for Johnson on the 25-man roster.

"I was close to Lyle and I looked up to him," Goldschmidt said. "He's been here my whole career and he's been so helpful in every facet of the game. We talked about everything. He taught me so many things that I wouldn't have been able to learn on my own, and I wouldn't be where I am now if not for him. So obviously it's sad to see him go, but it's part of the business."

Johnson, acquired Sunday in a trade with Houston, started at third base. He gave the D-backs a 7-0 lead in the fifth inning with his second career slam. Johnson became the first player in the Diamondbacks' 15-year history to hit a grand slam in his first game with the club.

Johnson connected after a two-out intentional walk to lefty-swinging Miguel Montero. At that point, Montero was 8 for 15 lifetime against Harang.

In his previous at-bat, Johnson grounded into a double play with the bases loaded.

"I had a chance earlier in the game to do something and drive some runs in, and I kind of let the guys down. So I wanted to make up for that," Johnson said. "It's not that I was trying to hit a home run, but anytime a guy gets walked in front of you on purpose, you want to go up there and get a big hit.

Trevor Cahill (9-9) allowed a run and six hits over six innings with four strikeouts and three walks. The right-hander, acquired from Oakland in a multiplayer trade last December, is 3-0 with a 1.85 ERA in four career starts against the Dodgers.

Cahill, who allowed first-inning runs in each of his previous seven outings, gave up a leadoff walk to Mark Ellis and a single by Juan Rivera — who came in 1 for 15 against the right-hander. But Matt Kemp struck out and Andre Ethier grounded into a double play. Ethier, who had 55 RBIs in his first 63 games to lead the NL, has only six in 29 games and 102 at-bats since then — and none in his last nine contests.

NOTES: 3B Hanley Ramirez was 0 for 4 with a stolen base in his first home game for the Dodgers since they acquired him and LHP Randy Choate last Wednesday in a trade that sent Nathan Eovaldi and minor league RHP Scott McGough to Miami. In his 18 previous games at Dodger Stadium, Ramirez batted .388 with three homers and 10 RBIs.