Josh Collmenter got the starting nod when Saunders was scratched, and he set the tone by allowing just one run on three hits over four innings while fanning six.
Brad Ziegler, Craig Breslow, Bryan Shawn and David Hernandez followed Collmenter to the mound, and the quintet combined for 10 strikeouts.
Not only that, but Ziegler and Hernandez each picked up their first Major League hits in the process.
"Nine innings of one-run ball, 10 strikeouts from our bullpen -- that's a pretty impressive effort," Arizona manager Kirk Gibson said. "Couple of hits out of them. It turned into a good night for us."
Not so much for Saunders, though it is possible that the injury is not serious.
"It was just one of those weird fluke things where I just couldn't get loose," Saunders said. "Maybe I slept on it wrong or something like that. I felt great my last outing, felt great in my bullpen session on Wednesday, so I think this is just kind of a fluke thing. Strength-wise [the training staff] said I was off the charts, so I'm not worried about anything structurally."
Collmenter, who had not started since April 24, threw 85 pitches in his four innings of work, the most he'd thrown since tossing 98 on April 19.
"He's so funky," Cubs manager Dale Sveum said. "He's a guy you need to face three, four or five times before you get a good reading on that arm slot."
The Cubs were clearly flummoxed by Collmenter, who made a seamless transition into the emergency start.
"Mentally, it's probably way tougher than physically," Ziegler said of Collmenter. "He can get loose and go out and pitch, but it's just the idea that you go down to the bullpen, you relax because you're not expecting to get loose for five or six innings and all of a sudden he's got to turn it on right away."
Collmenter was able to leave with a lead thanks to a two-run homer by Jason Kubel in the fourth. Kubel's blast came on a 3-0 count, a pitch that Gibson likes to turn his hitters loose on.
"Just good execution," Gibson said. "That's not as easy as you think it is, to be standing up there at 3-0 and execute like that."
The D-backs added to their lead in the fifth when the red-hot Aaron Hill stroked an RBI single.
Then in the sixth, Arizona chased Chicago starter Jeff Samardzija (5-6) when Miguel Montero smacked a two-run triple that gave Arizona a 5-1 lead.
Things got downright giddy in the D-backs dugout when first Ziegler and then Hernandez picked up their first Major League hits.
Ziegler grounded a single to center in the fifth and wound up coming around to score his first run.
Then in the eighth, Hernandez blooped a single to right. When he met with reporters after the game, he did so with a bat in his hand and a smile on his face.
"It just puts another option in Gibby's mind," Hernandez jokingly said of his performance at the plate. "If we ever need an extra pinch-hitter, I'm available, Ziggy's available. I expect to see myself on the lineup card on the hitting side now."
It was just Hernandez's fourth career plate appearance. Did Gibson tell him not to swing the bat, as a lot of managers do when a pitcher has little experience at the plate?
"I don't know what he was saying," Hernandez said. "He was yelling at me, but I could not hear him. I think he said, 'Take the first pitch.' I told myself I was going to swing once and it was 0-2, so I swung."
And like everything else for the bullpen on this night, things worked out just fine.