"It's pretty cool," Walker said. "I was born and raised in Milwaukee and have been watching the Brewers my whole life."
• Brinson, Hader added to 40-man roster | • Brewers' Top 30 prospects
The Twins wound up selecting Walker in the third round, and he rose as high as Triple-A Rochester in 2016, ranking second in the International League with 27 home runs while leading it with 202 strikeouts.
Walker, a catcher in high school, has mostly played the outfield corners as a pro and is most natural in left. The Brewers, however, are open to seeing whether he can handle first base, where they face an immediate decision on arbitration-eligible slugger Chris Carter, and a long-term one with no standout prospect at the position.
Walker ranked 15th on MLBPipeline.com's list of the top Twins prospects before Friday's move.
"He has among the strongest power grades of any hitter in professional baseball from our scouting reports," Brewers general manager David Stearns said. "Whenever you see a tool like that that's readily available, you take notice."
Of the potential for a try at first base, Stearns said, "That's an added benefit."
Walker comes from an athletic family. He is a second cousin of former Major League infielder Damion Easley, and Walker's father, also named Adam, briefly played in the NFL for the Vikings.
After playing baseball (as a catcher), basketball and football at Milwaukee Lutheran, Walker attended Jacksonville University before the Twins drafted him. In five Minor League seasons, Walker has hit .251/.310/.486 with 124 home runs and 744 strikeouts in 2,449 plate appearances.
The Twins added Walker to their 40-man roster at this time last year, and he spent the season as a 24-year-old at Triple-A. His on-base percentage slipped to a career-low .305, but his 27 homers were only four off the career-high 31 he hit at the Double-A level in 2015. He compiled 202 strikeouts in 531 plate appearances.
Walker acknowledged he will have to improve his plate discipline.
"I saw a lot of my friends and teammates get called up. Unfortunately, I wasn't one of them at the time," Walker said of his Triple-A experience. "Like they say, one call away. I'm just trying to keep working this offseason and come into Spring Training ready to go. I would like to make this the year."