Witt, who is ranked No. 2 in ESPN's top prospects for the 2022 season, was given the news Tuesday by Royals manager Mike Matheny and general manager J.J. Picollo as some of his teammates watched on.
"All the guys were congratulating me," Witt told reporters, according to MLB.com. "I can't really put words to the feeling how it was. My stomach sank. Tears came to my eyes. It's something I'll never forget."
The 21-year-old, whose regular position is at shortstop, fills a need at third base. Adalberto Mondesi, who had been penciled in at third, will instead play shortstop, and Nicky Lopez will be at second base.
Witt, the No. 2 pick in the 2019 MLB draft out of high school, has a .406 batting average during spring training, with three home runs, 11 runs, 8 RBIs and 2 stolen bases in 32 at-bats.