The 15-year veteran has been mentoring young teammates since spring training. And after a rough patch on the mound in April, he's off to a splendid start himself in May.
Arroyo kept Milwaukee at bay with off-speed stuff, allowing an unearned run and five hits in 7⅓ innings, to lead Arizona past the Brewers 3-2 on Wednesday.
Paul Goldschmidt hit a two-run homer for the second successive game for the Diamondbacks, who have won five of seven after starting the season 8-22.
Arroyo (3-2) has been one of the sparks, going 2-0 with an 0.87 ERA in his past three starts.
"He's throwing the ball good. He's been trending in this direction and in total command today," manager Kirk Gibson said.
Wily Peralta (4-2) allowed 11 hits, tying his career high, and two runs in six innings. The right-hander had trouble all afternoon locating his pitches, including a fastball that can reach 96 mph.
Arroyo doesn't throw nearly that hard, but he was even more effective against the free-swinging Brewers.
"It's hard as a hitter to go up that way. You think you get a fastball and then you sit off-speed," manager Ron Roenicke said. "The more swingers you have in your lineup, the more you'll have trouble with him."
Arizona stranded 13 runners, including leaving men at third three times through the seventh.
The right-handed Arroyo made up for Arizona's shortcomings at the plate with his outing on the mound. He made Jonathan Lucroy flail on an 86 mph sinker to start the seventh with a strikeout, and ended the inning by striking out Mark Reynolds on a slider.
It's a far cry from a few weeks ago when Arroyo didn't make it out of the fifth and allowed a combined 18 hits and 14 runs in back-to-back outings against the Mets and Cubs. He's backing up his encouraging words to teammates with solid starts again.
"You try to do all the little things and field your position," Arroyo said in recounting talks to younger players. "All those types of things matter. Especially for a guy like me, I'm not overpowering so I have to take everything I can."
Reed struck out Reynolds swinging on a high fastball to end the game.
The Brewers are now 2-6 after opening with a big league-best 20-7 record. With third-place hitter Ryan Braun out with an oblique injury and cleanup hitter Aramis Ramirez slumping badly, the offense has been choppy -- leaving less margin for error for a pitching staff off to a strong start overall.
"I know the lineup's not the same, but we still have enough guys in there that I think we should be scoring some runs," Roenicke said. "We'll get it going, we'll figure it out."
Arizona escaped a jam in the eighth after the Brewers put two on with one out. Pinch-hitter Rickie Weeks then lined a single off reliever Brad Ziegler that loaded the bases for Carlos Gomez -- who hit the next pitch sharply into an inning-ending 6-4-3 double play that elicited groans from hometown fans.
Arizona is finding its way on the road. Goldschmidt hit an 0-1 pitch for his seventh home run of the year after Martin Prado led off the third with a single.
"This whole road trip I think our bats are getting better. We're starting to drive the ball a little bit," Gibson said. "We're starting to get better."
Arroyo is among eight active pitchers to have appeared in a game at Milwaukee's old home, County Stadium. Miller Park opened in 2001. ... 3B Ramirez got a day off. The veteran is hitting .089 (5 for 35) since April 17. ... Both teams get a day off Thursday. Brandon McCarthy (1-5) starts for the Diamondbacks on Friday when they open a three-game interleague series in Chicago against the White Sox. Brewers ace Yovani Gallardo (2-1) opens a three-game series against the visiting New York Yankees.