Infielder Irving Falu was called up from Triple-A Omaha to take Betancourt's spot on the roster. The move also established Chris Getz, who had been sharing second-base duties with Betancourt, as the everyday second baseman.
Betancourt injured his ankle while taking a swing during a Spring Training game about a month ago, but had continued to play.
"It wasn't getting any better. We injected it and he felt better for a little bit, but it's just progressively getting worse and worse," manager Ned Yost said.
At the moment, Johnny Giavotella, who finished last season as the Royals' second baseman but was sent to Triple-A Omaha in Spring Training, does not figure in the scenario.
"He very well could, [but] the way Getzy is playing, bringing up Gio would mean that he would be the bat off the bench right now, and I don't want to do that. I want to keep him playing," Yost said.
Giavotella, after a slow start for Omaha, has a 14-for-33 (.424) spurt going in seven games through Wednesday, and his overall average was up to .301. Getz was batting .326 in 15 games for the Royals and delivered the game-winning hit on Wednesday in Detroit.
Also Falu is an experienced shortstop, a position that Giavotella has not played.
This is a big breakthrough for Falu, 28, who has been in the Royals' organization since 2003, but has never played in the Major Leagues.
Falu was hitting .306 in 21 games for Omaha, with one home run and 10 RBIs. This is his fourth season with Omaha, and last year, he batted .301 for the Storm Chasers and played second base, third, shortstop and right field.
"I've been impressed with Irving Falu from the minute I saw him two years ago," Yost said. "He's actually a perfect utility guy; he's a switch-hitter that can swing the bat both ways, can play just about any position on the field. So it just gives us depth at all positions."
A switch-hitter from Puerto Rico, Falu is the cousin of former Royals infielder Luis Alicea. Another Omaha possibility, infielder Tony Abreu who has Major League experience, is injured.
Betancourt has battled the injury while playing in 15 games, mostly at second base. He's hitting .280.
"It's altered his gait, it's altered his swing," Yost said. "He's starting to get some quad tightness now because of running funny."
Yost said test results on Thursday determined that Betancourt had a high ankle sprain, which generally takes longer to heal than a lower sprain. Betancourt will stay off the ankle for about 10 days to allow the inflammation to subside.
Betancourt's 15 days began on Wednesday. To make room for Falu on the 40-man roster, closer Joakim Soria was moved from the 15-day to the 60-day DL. Soria is out for the season after elbow surgery.
Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.