TORONTO -- About a week before Memorial Day, Brandon Hyde called Ryan Mountcastle into the visiting manager’s office at Nationals Park and sat the rookie slugger down. A day earlier on May 22, Mountcastle had rocketed his first career grand slam off Jon Lester as part of the Orioles' five-run first inning in a game they’d go on to lose, 12-9. A season filled with similar defeats was supposed to be offset by the development opportunities for young players like Mountcastle, whom the O's consider a long-term piece.

But to that point, Mountcastle, fresh off a sensational 35-game cameo in 2020, was floundering. He walked into Hyde’s office carrying a .228/.251/.361 slash line and four homers over 43 games, and he was still struggling to acclimate himself in left field. Hyde’s message was forceful but direct, and ultimately inspiring.

“He tried to light a fire under [me] a little bit,” the 24-year-old Mountcastle said this weekend during the Orioles’ season-ending series against the Blue Jays. “He basically said, ‘I believe in you and I think you can do this. Now it’s time to get it going.'”

Months later, both Hyde and Mountcastle pointed to that moment as a turning point in the ascendant slugger’s season, one of the most exciting and productive by a rookie in the Majors. Climbing out of those depths with a productive final four months, Mountcastle is MLB's rookie leader in homers and among its leaders in RBIs, slugging percentage and total bases, and he's in the thick of a deep, jumbled race for the American League Rookie of the Year Award.

“I thought, ‘All right, it’s time to go. I gotta figure it out.' And I think I eventually did,” Mountcastle said. “He’s a great coach. I love the guy. I like being told, ‘Hey, figure your [stuff] out.' That’s what I respond to.”

All told, Mountcastle hit .267/.333/.544 over his final 100 games to climb out of his early season hole, going into Sunday's season finale against the Blue Jays at .255/.310/.490 with 33 homers, 89 RBIs and a .799 OPS in 143 games. His shattered Cal Ripken Jr.’s franchise rookie home run record, shifted full-time (and more successfully) to first base and generally made strides in areas the Orioles hoped to see progress in, namely his defense and plate discipline. Mountcastle might always be more of a free swinger, but the O's are pleased with how he more than doubled his walk rate over his final 100 games -- and with the production that followed.

“He’s matured an incredible amount over the course of this season," Hyde said.

"Can we start talking about him more for Rookie of the Year, please? I think he has been [overlooked] because of our record, and maybe we’re not on national TV as much, I don’t know. But I do think he should be heavily considered for that award for what he’s done, and he has my vote.”

Hyde focused on Mountcastle’s power and team high in RBIs, noting how that production came in the hyper-competitive AL East. Those are the pillars of Mountcastle’s case, but they are not the only factors voters will consider. Even with his strong finish, Mountcastle’s early defensive issues and deflated on-base percentage weigh down his WAR by both Fangraphs' and Baseball Reference’s calculations.

Per Fangraphs, Mountcastle ranks tied for 13th in WAR among AL rookies, well behind Tampa Bay’s Randy Arozarena and Wander Franco, Rangers slugger Adolis Garcia, Astros righty Luis Garcia and Indians closer Emmanuel Clase.

However Mountcastle fares in the voting, the Orioles view his development as one of the main bright spots from what will go down as the second-losingest season in team history. He looks like a fixture in the middle of their lineup for years to come.

“Especially after that first month, I thought I might never hit a home run again,” Mountcastle said. “It’s helped me grow as a player and as a person, too. Going through struggles like that definitely helps you out in life and makes you a better person.”