"A day like that," said Nieuwenhuis, who led the way with six RBIs, "everybody goes home happy."
Everybody in a Brewers uniform, that is. Broxton had three hits, three runs and three RBIs and has now reached safely in all 11 of his Cactus League games. He paired with Shaw for back-to-back home runs off Iwakuma in the second inning. Arcia logged his first three RBIs of the spring. Jesus Aguilar walked three times and scored four runs.
Since the scoreboard has only a single digit for each inning, Milwaukee's 10-run fourth was marked simply with the number 1.
"I mean, it's Spring Training, you know? That's the big thing," Brewers manager Craig Counsell said. "Don't draw conclusions from it. Some guys swung the bat well, and that's always a good thing."
Brewers starter Junior Guerra, meanwhile, surrendered only one hit -- Ben Gamel's first-inning home run -- in four innings. The Brewers answered Gamel's solo shot to center field by scoring eight runs before the end of the third.
Iwakuma, making his third spring start, allowed seven earned runs on six hits in 2 2/3 innings.
"Overall my timing, my balance, I couldn't get my lower body to sync to my upper body," said Iwakuma, who won 16 games last year as Seattle's No. 2 starter. "I couldn't get the feel for really any pitch that I had. Nothing was working. I have nothing to say today that went well."
Mariners rookie first baseman Daniel Vogelbach ended Milwaukee's string of 24 straight runs with a two-run homer in the seventh, his first of the spring.
Mariners Up Next: James Paxton faces the White Sox top pitching prospect, right-hander Lucas Giolito, in Tuesday's 1:10 p.m. PT game at Peoria Sports Complex. Nick Vincent, Dan Altavilla and lefty Dillon Overton are among the scheduled relievers. The game will be broadcast live on MLB.TV.
Brewers Up Next: The Brewers face the World Series champion Cubs for the first time on Tuesday at Sloan Park in Mesa, Ariz., with Zach Davies on the mound for Milwaukee against Chicago newcomer Brett Anderson. The 3:05 p.m. CT game will air on Gameday Audio.
Watch every out-of-market regular-season game live on MLB.TV.