Minnesota United is preparing to go without its team captain for probably a month.

Center back Francisco Calvo, who played arguably his best game of the season in Saturday's 1-0 victory against Vancouver but followed it with a struggle Wednesday at LAFC, likely will be the Loons' lone representative at this summer's World Cup in Russia, which starts June 14. While his departure date to join his Costa Rica national team isn't set yet, he will most likely join the training camp the last week of May in hopes of making the final roster for the tournament.

If Costa Rica were to go all the way, the Loons could be without the defensive leader for a half-dozen games. Costa Rica's group stage matches last through June 22, at the very least.

But United does have options for his replacement. Michael Boxall, the other starting center back, will hold down the fort while either Brent Kallman, Wyatt Omsberg or Bertrand Owundi Eko'o battle it out for Calvo's place.

Kallman looks like the lead candidate as the most experienced of the bunch. He did endure a minor shoulder injury in a scrimmage last week that kept him out of the lineup against Vancouver.

"I'm just trying to get myself as close to game fitness as I can," Kallman said ahead of the scrimmage. "Trying to make sure I'm focused and ready because my time for games might be coming really soon here. So I really would like to step in and not miss a beat and help us get some points while Calvo is away."

Omsberg, a rookie, has also seen some playing time this year for United as well as on loan to the United Soccer League's Tulsa Roughnecks. He said the loan was a good experience, just to gain more minutes and game situations in front of a decent crowd and solid opponents. He could go back to Tulsa at any point, but while he's back with United now, he said he works every day in practice to learn from the likes of Calvo, Boxall and Kallman.

"I think the USL games will be a big way to try and get ready," Omsberg said. "Stay sharp, stay fit and hopefully be ready if my name does get called."

Owundi has yet to play since joining the Loons from his native Cameroon and is coming back from a hamstring injury.

Ibarra on the rise

All four times Miguel Ibarra has gotten himself on the stat sheet for Minnesota United this season (three assists, one goal), they've all been on game-winners. In nine games this season, he's already one assist and two goals away from equaling his 2017 total in 29 games.

"I think I'm getting better every game," Ibarra said after the Vancouver game. "I mean, my confidence right now is really up there. I know I didn't have a good year last year. So starting in the offseason, I was just making sure I worked. Christian [Ramirez] really helped [me] get really fit in the offseason. So doing that [at home] in California and coming back early and making sure I was fit. And now the hard work is paying off."