In the fifth inning of a 9-7 victory over the Brewers, there was a runner at first base when Betancourt went behind the bag to backhand Yovani Gallardo's grounder and, heading toward center field, he threw the ball behind his back to shortstop Alcides Escobar.
Escobar grabbed the ball, stepped on the base and relayed to first baseman Eric Hosmer for a double play.
"Yuni's been playing spectacular at second base and really at all the defensive positions, he's done a nice job, but he's really been impressive at second base," manager Ned Yost said.
Yost will choose between Betancourt and Chris Getz for the Opening Day second baseman.
Betancourt also contributed one of the Royals' five homers on a power trip day (the Brewers hit two). Hosmer hit two blasts, one to right field and one to left, to give him four in the Cactus League. Mike Moustakas hit his first homer.
"Everybody's ready to go. We just have to play the rest of the schedule out," Yost said. "But offensively ... everybody's ready to go."