Toward the end of Ryan Mountcastle's much-anticipated MLB debut, Orioles ace John Means approached him with the intention of “giving him some crap.” It was the good, camaraderie kind, the kind rookies get for getting to The Show, like the way Mountcastle’s teammates tricked him into running onto the field without them before Friday’s 8-5 loss to the Red Sox.

Except this particular ribbing had to do with what Mountcastle did once he was in between the lines.

“He might have walked 10 times in his whole Minor League career,” Means explained afterwards. “And he walks two times in his first Major League game?”

Thus proving the irony of Mountcastle’s debut wasn’t lost on those in the home dugout. For years, the Orioles fawned over the potential in Mountcastle’s bat while hammering home his need to draw more walks; then this summer, they delayed his promotion in favor of more reps at their alternate site in Bowie, Md., where plate-discipline drills were a constant focus.

So it was with all that as a backdrop that Mountcastle walked twice in his first four plate appearances in the Majors, becoming the first Oriole player in 38 years to do so in his debut. It was a feat not accomplished since Glenn Gulliver in 1982, who was the only player to do so until the club’s No. 5 prospect (per MLB Pipeline) did it against the Red Sox on Friday.

“I thought those were two good at-bats,” manager Brandon Hyde said. “It was nice for him to get his feet wet tonight.”

Going forward, the Orioles’ plan is to run Mountcastle out there every day the same way they did on Friday, when he batted sixth and started in left field. He is expected to play mostly outfield in the Majors, though he could see time at first base and designated hitter as well, with Chris Davis sidelined for the foreseeable future. The O’s placed Davis on the injured list Friday with what they called left patellar tendinitis; there is no timetable for his return.

The club’s reigning organizational player of the year, Mountcastle, 23, hit .312/.344/.527 with 25 homers at Triple-A Norfolk last season, earning International League MVP Award honors. Mountcastle is the second of the club’s Top 15 prospects to debut this season, along with No. 13 Keegan Akin. Other prospects like No. 10 righty Dean Kremer and No. 23 Rylan Bannon could also arrive before season’s end.

“I feel like I'm ready to go,” Mountcastle said Friday afternoon. “This game is tough as it is. So I think you're going to be developing your whole career. Trying to be the best player you can be and for right now.”

Before the game, the Orioles surprised Mountcastle with videos from his family congratulating him on his promotion. He then ran out for his first defensive inning alone, realizing only after he crossed the foul line the prank his teammates had pulled. The baseball part was comparably low-key: Mountcastle worked a seven-pitch walk off Colten Brewer in the second, struck out in the fourth, flew out to right in the sixth and drew an eight-pitch walk off Josh Osich in the eighth. Mountcastle also handled two routine fly balls that floated his way in left without issue.

“I'm just going to go out there and play my game and not try to do too much,” Mountcastle said. “That's all I can do. I'm not going to be you know, trying to, you know, hit balls 800 feet. I'm just going to try to stay within my approach and keep doing [what] I've been doing.”

For weeks, the Orioles have hesitated to call up Mountcastle while their offense sputtered at the big league level, especially since José Iglesias (left quad) and Austin Hays (displaced rib fracture) landed on the injured list. Baltimore had been giving the lion’s share of left field reps to Dwight Smith Jr. and utility man Pat Valaika in recent weeks. That onus now falls on Mountcastle, whom the Orioles have worked hard to find a defensive home since making him their first-round pick out of the Florida high school ranks in 2015. Throwing issues forced his move from shortstop to third base as a younger prospect, then first base and finally left field. Mountcastle played mostly first last summer at Norfolk, but had been getting reps in left while at the Orioles’ alternate training site.

"I just want him to be as comfortable as he could possibly be. Want him to feel like he belongs here," Hyde said. "I think he's a confident guy. I think half of the battle is to feel like you belong here and I think he feels that way."