But 16 days and 15 games later, the club has won just three times, going 4-11 over the span.
Joe Saunders is a perfect microcosm for the team's struggles in May.
After April, the lefty boasted a National League low 0.90 ERA. But in May, the 30-year-old has struggled mightily in three starts, surrendering a combined 14 earned runs in 14 2/3 innings.
Saunders and the D-backs will look to get back on track when they visit the Royals on Friday in the opening game of the weekend Interleague series.
Arizona swept Kansas City last year, with Saunders earning one of the wins by tossing seven innings and allowing two runs on six hits in a 7-2 D-backs victory.
In his last start, Saunders gave up six earned runs on 10 hits over five innings in a loss to the Giants on Mother's Day.
"It's pretty frustrating, and you can see the frustration on everybody right now," Saunders said. "We are going through a bad stretch. It's frustrating in every aspect. We just have to get through it."
Going for the Royals will be Luis Mendoza, who is coming off his best outing of the season.
The 28-year-old allowed one run on seven hits over 5 2/3 innings in a 9-1 victory over the White Sox on Sunday. He was inserted into the game after just 13 pitches from starter Danny Duffy, who left the game with elbow tightness.
"I can't imagine what those guys do. As a position player every once in a while you might get thrown in to pinch-hit or pinch-run, but as a pitcher, when you're down there in your mindset you're not ready for a game like that," Royals outfielder Jeff Francoeur said. "That was unbelievable what he came in and did."
Royals: Coleman, Teaford promoted
The Royals on Thursday recalled left-hander Everett Teaford and right-hander Louis Coleman from Triple-A Omaha and optioned right-handers Nate Adcock and Vin Mazzaro.
The move gives manager Ned Yost needed flexibility with his pitching staff.
"We need the arms, it's as simple as that," Yost said. "Our bullpen guys have been going two days on, one day off, two days on. We need extra protection in the middle, and we need protection in the long guy. We can't get these guys any type of break."
D-backs: Bauer promoted
The D-backs promoted top pitching prospect Trevor Bauer to Triple-A Reno on Thursday. He is slated to start for the Aces on Friday against Oklahoma City.
Bauer was Arizona's top selection (third overall) in the 2011 First-Year Player Draft.
In eight starts for Mobile, Bauer was 7-1 with a 1.68 ERA and he allowed just 33 hits in 48 1/3 innings, while striking out 60 batters.
Jarrod Dyson has scored 15 runs in 18 games as the everyday centerfielder since joining the club for a second time on April 27.
The D-backs are 100-120 all-time in Interleague Play, including a 53-60 record on the road. Last season, the D-backs swept the Royals.