The win, coming on the heels of a needed off-day following an ugly 3-7 stretch, also let Milone off the hook for an uncharacteristically inefficient outing.
The southpaw needed 103 pitches to get through just 4 2/3 innings after compiling at least six innings in 11 of his first 15 starts. In that time, Milone allowed three runs on six hits with a season-high four walks, including three in a row before his departure.
Oakland's bullpen, which allowed 15 earned runs in 18 2/3 innings on the last road trip, followed with 4 1/3 scoreless frames.
"I don't know," Milone said, "something was a little bit off. I wasn't able to throw it where I wanted to. It was just an uncomfortable feeling."
Luckily, the A's were just as wild.
They went down in order in the first, before pouncing on Arroyo and putting nine of their next 17 batters on base.
Brandon Moss jump-started the brigade with a one-out double in the second, sparking a base hit from Josh Donaldson and an ensuing two-bagger off the bat of Josh Reddick that plated the first run. Stephen Vogt, making his A's debut, contributed right away with a sacrifice fly for his first career RBI, and the A's would add four more in the third.
Donaldson highlighted that inning with a two-run homer, Yoenis Cespedes having already done his part by way of an RBI base hit. Seth Smith joined the fun in the fourth with a run-scoring single, and by the time the fifth came around, Arroyo was done.
And he was impressed.
"They just had a great approach against me, to be honest with you," Arroyo said. "I predicate my game on being able to play a mental chess match with guys and beating them to the move first. They just beat me to the punch. They had a nice approach. They did some things I didn't expect them to do.
"I wasn't surprised that they swung early. I was surprised at some of the pitches that they swung early on. Donaldson hit a first-pitch breaking ball out of the park after seeing a changeup his first at-bat and rolled one over to the shortstop for a hit. Things like that are a little quirky and off the beaten path. They flipped the tables on me tonight. I usually pitch off the beaten path, and they came at me with an approach that was a bit awkward."
It marked the veteran's shortest start since July 2012. Moreover, he hadn't given up more than seven runs since allowing eight to the Indians in 4 2/3 innings in July 2011.
"It's always nice to get those big leads," Donaldson said. "It's been one of those things here lately where we get the opportunities and haven't cashed in right away. Tonight the ones we had early in the game we were able to take advantage of.
"We have a lot of guys in our lineup that can do some damage, not just hitting home runs but getting on base. It's kind of funny, I look over there, and they have bigger names, but I feel we kind of resemble each other in a lot of ways. Both teams are fairly patient at the plate, and up and down the lineup you have guys that can do something at any time."
By record alone, the teams are indeed quite similar -- even dating back to almost a full year ago.
Since July 1, the A's are a Major League-best 102-60, marking a full season's worth of games, and the Reds are next in line with a 99-64 ledger.
"I don't think it's a coincidence," Donaldson said. "They've got some guys in the lineup that have a pretty good track record, and I feel like we have the same potential that they do, it's just guys who don't have a track record yet."
"It's trending," manager Bob Melvin said, "and we're going in the right direction, but it would be nice to be able do that from April through September."