The loss snapped Arizona's three-game winning streak and got their second half started on the wrong foot.
"We just didn't play good," D-backs manager Kirk Gibson said. "They kicked our butts in every aspect. We didn't execute in any phase of our game and it was disappointing."
Nothing was more disappointing than the performance of starter Ian Kennedy, who has struggled to find the consistency that allowed him to win 21 games in 2011.
The right-hander allowed seven runs on seven hits in lasting just five-plus innings. Not the kind of lengthy outing Gibson spoke about wanting from his starters with a stretch of 20 games in 20 days.
"Five innings, that's not going to get it [done]," Gibson said. "He was unable to execute his pitches, especially against Soriano. He's unable to throw his fastball where he wants to and his secondary pitches, which he threw very well last year when he got behind in the count, he's just unable to locate them. He's just a different pitcher right now."
Soriano seems to save his best performances for the D-backs.
In his career against Arizona, Soriano has hit .336 (43-for-128) with 16 home runs and 36 RBIs. Both of the homers came on first-pitch fastballs.
"I think you need to execute better against him," Gibson said. "He's a good veteran guy who's been around a long time. He's had success against us, it's our job to make him uncomfortable and not throw balls down the middle like that."
Kennedy obviously wasn't trying to throw the ball down the middle of the plate, but one of his biggest issues this year has been his lack of command and inability to put the ball where he wants consistently.
"I didn't make any of my pitches, so it didn't really matter," Kennedy said when asked what approach he was using with Soriano. "The changeup was over the plate for his first double. Right-down-the-middle fastball for the home run and then the second home run was down and in. He usually likes it down. The execution was terrible."
After watching Kennedy have nearly pinpoint control last year, catcher Miguel Montero is at a loss for why that has not been the case this year.
"It's hard. We've been trying hard. I know he's trying hard, it's just frustrating because you try to get into it and he just hasn't put it all together so far," Montero said.
Soriano's first homer led off the fourth inning and gave the Cubs a 2-1 lead.
One inning later, he widened the lead when he blasted a two-out, three-run homer that put Chicago up, 5-1.
The All-Star break apparently helped the veteran.
"I [felt] very good today," Soriano said. "Those four days, I cleared my mind and my body, too. The game that I had today, I hope I have a couple more like that and help the team to win."
For Kennedy, it's back to the drawing board.
"It's really, really frustrating," he said. "That's all I can tell you. I feel good one outing and then I don't know what happens the next outing. It's two completely different people. It's frustrating for me."
To add injury to insult, D-backs left fielder Jason Kubel was forced to leave the game in the seventh after he experienced tightness in his right hamstring.
"I had that little slip in the second inning," Kubel said. "[The field] felt slick all game long, it was pretty dangerous out there. I was hoping as the game went on, it would loosen up and get better, but it just got worse and worse."