DUNEDIN, Fla. -- Derek Shelton didn’t know the best way to tell Mitch Keller the good news. So he started with a series of questions.

How did your side session go today? How many pitches did you throw? How many do you think you’ll throw on the 30th?

The last question caught Keller off-guard. Why would he be thinking about March 30, which was two weeks away? Then, it clicked. It clicked that he would throw the first pitch of the season. It clicked that a dream had come true. It clicked that he’d be the club’s Opening Day starter.

“It was actually pretty emotional for him,” Shelton said before the Pirates' 7-1 loss to the Blue Jays on Wednesday. “He was pretty fired up. Those are special moments. This is a kid who was a very highly touted prospect and had to grind a little bit and discovered himself. It was a cool moment. Gave him a bottle of champagne and told him and [his wife] Clancy to enjoy it.”

"There’s a lot of people around me that have helped me along my way and through thick and thin — and through the good times, too," Keller said. "It’s really cool moment for everybody involved, not just myself. It’s really cool.

The decision, in some respects, was an inevitability. Keller is coming off the best year of his career, a season in which he logged career-highs in innings (159) and strikeouts (138), as well as career-bests in ERA (3.91) and FIP (3.88). Getting to this point, however, required Keller to wade through the desert of despair.

Keller, a second-round selection in the 2014 MLB Draft, flashed top-of-the-rotation stuff during his first couple of seasons, but he never put everything together. He struggled, and struggled hard. From 2019 to '21, Keller owned a 6.02 ERA across 170 1/3 innings. In '21, the Pirates sent Keller down to Triple-A Indianapolis.

In 2022, Keller underwent an evolution. He re-discovered his fastball velocity. He added a sinker. He added a sweeper. Keller re-invented himself on the fly, and following three seasons of tribulations, he finally found success.

“Everybody aspires to be an Opening Day starter at some point in their career, but for young guys coming up, I do think it’s something they can look and say, ‘Hey, this is a guy who came through our system,’” Shelton said.

Keller wouldn’t have flourished without seeking this evolution -- and he’s continued to grow this spring, adding a cutter into his mix. But the 26-year-old’s most significant area of growth has been his mentality.

On multiple occasions last season, Keller discussed his growing confidence, his ability to be unshakeable in the face of tough situations. He admitted that, during the infancy of his career, he might have looked towards the dugout for someone to take him out of a game when things got rough. In 2022, by contrast, Keller exhibited the bravado to finish what he started, to pitch until his manager took the ball from his hands.

Shelton pointed to Keller’s outing on Sunday against Atlanta as an example of how the right-hander can navigate tough waters. Keller sputtered out of the gate, allowing a solo home run in the first inning, then allowing an RBI single in the second. Early in his career, Keller might have let those two rough frames affect the rest of his outing. Instead, Keller retired the side in the third and fourth innings, striking out two batters in each frame.

“Now, he’s taking charge,” Shelton said. “You really saw it in the third and fourth innings. That may have been the best stuff I’ve ever seen him have. He went right back out after people.”