"The first pitch was a breaking ball [from starter Luke Putkonen] and the runner was moving from first, so I took it. The second pitch was the same breaking ball, so I saw it well and put a good swing on it," said Kjeldgaard, who also homered on a first-pitch fastball from Cubs reliever Nick Struck in the fourth.
"I was just swinging at good pitches today and they happened to go out. ... We play Spring Training in Arizona and the parks are bigger, but the ball always flies good here."
The Alberta-born Kjeldgaard also went deep Wednesday in his Fall League debut. He's no stranger to the longball, having averaged 19 homers in his first four seasons in the Minors.
Kjeldgaard slugged a dozen this year, playing only 81 games, 48 at Double-A Huntsville.
"For me, missing time, I came here to get more at bats and make up for the time I lost," he said.
As good as Milwaukee's farmhand was on Saturday, he was outdone by a pair of Solar Sox. Jonathan Singleton (Astros) and Javier Baez (Cubs), the top prospects in their respective organizations, went yard to account for five of Mesa's eight runs.
Desert Dogs starter Nick Bucci (Brewers) gave up just Singleton's two-run shot over the first three innings, while reliever Santo Manzanillo (Brewers) surrendered four runs in the fifth frame, three on Baez's blast.
Baez and Singleton, both among MLB.com's Top 100 prospects, already have two homers apiece.
Coming off a four-RBI night, Astros prospect George Springer went 2-for-2 with a walk, drove in two runs and scored once for the Solar Sox.
Kevin Kiermaier (Rays) was 3-for-4 with a double out of the ninth spot in the Phoenix lineup, raising his average to .455.