KANSAS CITY -- Royals games will return to full capacity at Kauffman Stadium starting on May 31, when they host the Pirates, the club announced on Tuesday. Single-game tickets will go on sale at 10 a.m. CT on Thursday on royals.com.

Kansas City began the season at 30 percent capacity and expanded to 17,400 fans at The K at the beginning of May. With the new CDC guidelines and city protocols, the Royals were able to work with Mayor Quinton Lucas, Dr. Rex Archer and the Department of Health, along with Jackson County, on re-opening the stadium.

“It was a shame last homestand that we did the way we did [going 0-7 against Cleveland and the White Sox], because it was a great atmosphere for us,” manager Mike Matheny said. “The fans were into it. They were really into it, actually. You could tell, every pitch that didn’t get called our way, there was a lot of edge to them. So hopefully, as we get close to that date when we do have full capacity, we start playing better baseball again. I know that’s exciting for our fans and helps put people in the seats. But the ability to have that kind of Major League atmosphere is something we’re all looking forward to.

“This game at this level is driven by our fans. It’s a huge deal. … The last homestand, that energy, it’s hard to fake that. ... that’s irreplaceable.”

Most of the health and safety protocols from the beginning of the regular season will remain in place, including restrictions on bags and outside food in the stadium. Tickets and parking passes must be purchased in advance and will only be available on mobile devices via the MLB Ballpark app, and the stadium will continue to be cashless -- a credit or debit card is needed to make on-site purchases.

But masks will no longer be required for vaccinated fans. Face coverings are still recommended for non-vaccinated fans.

Zimmer returns, Mondesi to Triple-A

The Royals reinstated reliever Kyle Zimmer off the 10-day injured list on Tuesday, giving a big boost to the back-end of the bullpen. The right-hander had been sidelined since the beginning of May with a left trapezius strain, and he had made two rehab appearances with Triple-A Omaha this past week.

Zimmer was 2-0 with a 3.38 ERA in 11 games (13 1/3 innings) entering Tuesday's series opener against the Brewers. He also had one save and had pitched himself into a high-leverage role with the Royals, so having him back can take some of the load off Scott Barlow and Josh Staumont. Once Jesse Hahn (right shoulder impingement) returns from his rehab assignment -- and reports have been positive -- the bullpen will look like it did at the beginning of the season.

“Jesse seems to be doing really well also, but to have Kyle back right now is a big deal for us,” Matheny said. “This gives us opportunities when we do beat up a couple other guys. We’ve been beating up Barlow and Staumont. Kind of spread the wealth from those leverage situations. That’s the place Kyle Zimmer has pitched himself into.”

In other rehab news, shortstop Adalberto Mondesi (right oblique strain) was transferred to Triple-A Omaha. He’s full go on defense and at the plate, swinging from both sides, so it’s just a matter of getting his timing down and making sure he’s 100 percent before he joins the Royals after hitting the IL a day before the season began.

At Double-A Northwest Arkansas, Mondesi went 3-for-12 in four games with one home run and three RBIs.

Standing O for LoCain

It wasn’t the first time that Brewers outfielder Lorenzo Cain has returned to Kauffman Stadium as an opposing player, but Royals fans still made the former Kansas City fan favorite feel special when he came to the plate on Tuesday night.

Cain got a big standing ovation from the 9,298 fans in attendance at The K, and he tipped his helmet to all of them, gesturing around the stadium and to the home dugout to acknowledge his former teammates. The 2014 American League Championship Series MVP was an integral piece to the Royals’ back-to-back World Series appearances in 2014 and ’15, and even though he left after the 2017 season for free agency, the fans still let him know how much he means to them when he has returned.

He also got a big hug from catcher Salvador Perez when the two chatted with Whit Merrifield in the outfield before the Interleague series opener.