Moustakas raked the 386-foot shot off Cardinals star Adam Wainwright Wednesday in St. Louis. The game was shortened due to rain, forcing players off the field after the seventh inning.
"That was the game really for us offensively."
Lorenzo Cain and Yasmani Grandal began the game with back-to-back singles for the Brewers. Brewers star Christian Yelich lined out to center field in the next at-bat. Keston Hiura followed by scoring Cain on an RBI single, prompting Moustakas' walk to the plate.
He fell behind in the count 0-2 against Wainwright before ripping a 76.2-mph curveball over the right field fence. The three-run shot had an exit velocity of 101 mph, according to Statcast. The long ball also gave the Brewers a 4-0 lead, which they would not surrender.
Hiura plated Yelich with an RBI double in the top of the fourth frame. The Cardinals answered with two runs in the fifth inning and another in the sixth inning, but could not close the gap.
Moustakas was 1-for-1 with three RBIs, three walks and a run scored in the win. Hiura was 2-for-4 with two RBIs and a run scored for Milwaukee.
Brewers starter Adrian Houser picked up his sixth win of the season by allowing six hits and three runs in 5.1 innings of work. Wainwright took his ninth loss of the year after allowing eight hits and five runs in 5.0 innings for the Cardinals.