SURPRISE, Ariz. -- One of the feel-good stories of camp, the surprising success of right-hander Kyle Zimmer, is becoming more real every day.

Zimmer’s strong spring -- five outings and a 0.00 ERA -- has put him firmly in the mix for a bullpen spot on the 25-man roster.

“There’s a fit there,” manager Ned Yost said. “Let’s see if there’s a puzzle piece left.”

None of this seemed possible a year ago. Royals fans know Zimmer’s story well: A first-round pick in 2012, Zimmer has had to overcome multiple injuries, surgeries and disappointments. He was dropped from the 40-man roster, then tried to resurrect his career through the Driveline Baseball program last summer.

The Royals signed Zimmer back to the 40-man roster last fall, but the big test came this spring, when he returned to the mound. So far it’s all clicking. His fastball is back up to 96 mph, and his curveball has been unhittable at times.

“I think he has been very surprising,” Yost said. “For me, it’s been an eye-opener. He came in, and you heard about these improvements he’s made, but hey, I got to see it. His first couple of side sessions were [just] all right.

“So then we see him on the mound, and each time out, he’s gotten better. He’s thrown himself legitimately into the mix. You root for someone like that, who has worked so hard to get here. But you don’t expect it to happen. But you hope it works out for him, and it is working out.

“His fastball is up to 96 and his curveball has been really good. It’s a legit breaking ball. You go up and down our bullpen roster, and everyone has their strengths and weaknesses, but no one else has that [curveball]. He’s got that bottom-falling-out breaking ball. Boom.”

Zimmer has tried to keep his excitement over potentially making the roster in check.

“But in my head, that’s what I’ve been going for since I showed up, to be on that 25-man roster,” Zimmer said. “But then, I really am trying not to think about what it will take to be on the roster. I have faith I belong on this team, on the 25-man roster. But there are so many aspects to [roster construction] that are out of your hands. I’m not going to play GM or manager -- we got guys who are really good at that. But yeah, in 10 days I want to be on that plane going north.”

Zimmer is one of several candidates vying for a spot in the bullpen. Wily Peralta, Brad Boxberger, Jake Diekman and Tim Hill are virtual locks to be part of what likely will be an eight-man bullpen. Kevin McCarthy seems almost a sure thing. Rule 5 Draft pick Sam McWilliams probably has done enough to merit a roster spot. Jorge Lopez, if he doesn’t win a job in the rotation, will go to the bullpen. That may be the case for Heath Fillmyer, too. Non-roster invitee Michael Ynoa is having a solid camp.

In other words, there will be some tough decisions ahead for the organization.

“But [Zimmer] is right there in the middle of it,” Yost said.

In the meantime, Zimmer will try to keep building his case.

“Each time out I’ve gotten more comfortable,” he said. “My mechanics are cleaner, the sequencing is better. It all leads to more strikes and better life on my fastball, better break on my curveball.

“I was trying to ease into it early in camp, and I think I did a good job of that, not overthrowing right away. Now I’m just letting it go and just competing. The ball is coming out really well, and I’m bouncing back with no problem. That’s the main thing. I feel like I could pitch every day.”