No matter if you're a future Hall of Famer or just getting a cup of coffee, you never forget your Major League debut. They are always unforgettable for the players making them, regardless of the outcome, context or circumstance. And sometimes they offer glimpses of greatness to come.

They are also the types of milestones in large supply lately for teams like the Orioles, who are geared toward the future and offering opportunity in droves. This is why their 2021 season has been full of nights like Friday, when right-hander Marcos Diplán debuted during the club’s 10-6 loss to the Rays at Oriole Park.

With two months of the season still to play, Diplán became the 14th Oriole to make his MLB debut already in 2021 (and second in as many games), and the 21st rookie to appear for the club this season. More are likely to come through August and September.

"When guys make their debuts and are in a Major League stadium for the first time, it's a really special feeling," Baltimore manager Brandon Hyde said. "I'm sure their hearts are beating super fast."

Here is how they fared in those moments, along with a running list of all the O's debuts this year:

Marcos Diplán, RHP
Prospect ranking: Unranked
Debut date: Aug. 6
The Orioles acquired Diplán off waivers from the Tigers in an under-the-radar move at the 2019 Winter Meetings, and they were impressed enough with him this year to send the righty to the Futures Game alongside Adley Rutschman. Diplán, 24, enjoyed one of the most successful debuts of the season Friday, retiring all five batters he faced to finish the Orioles’ loss to Tampa Bay. Diplán struck out three, including his first hitter, Ji-Man Choi.

Dusten Knight, RHP
Prospect ranking: Unranked
Debut date: Aug. 4
Knight, 30, spent eight seasons in the Minors with the Giants, Twins and Orioles, developing a reputation for performing on-field backflips after saves. He was promoted on Aug. 4 amid a bullpen shuffle, along with fellow rookie Marcos Diplán, then was called upon to pitch the eighth that night against the Yankees. Knight allowed hits to the first three batters he faced, but he then retired the next three in order, which included striking out Joey Gallo to end the frame. Knight allowed two runs in one inning.

Conner Greene, RHP
Prospect ranking: Unranked
Debut date: July 27
A former prospect in the Cardinals, Blue Jays and Royals systems, Greene, 26, worked the final two innings of a July 27 loss to close out Spenser Watkins’ first defeat of the season. A 28-year-old rookie himself, Watkins allowed more runs (four in four innings) Tuesday than he did in his first three starts combined, notably falling victim to a three-run Eutaw Street home run from Sandy León in the second.

That put the Orioles in an early hole they couldn’t climb out of against Sandy Alcantara, despite solo homers from Austin Hays and Cedric Mullins. Flashing a fastball as hard as 98.9 mph, Greene struck out his first batter, Magneuris Sierra, on three pitches, all above 97.5 mph. He ended up whiffing two without a walk in two innings, allowing a run on Jesús Aguilar’s RBI single in the eighth.

“He was really amped up that first inning,” Hyde said. “I liked the energy he brings on the mound. He’s definitely in the fight every single pitch.”

For Greene, the moment came after parts of eight seasons in the Minors, during which command issues twice plateaued him at Triple-A. He had a 7.39 ERA in nine games (three starts) this season at Norfolk before being summoned to the big leagues for bullpen depth this week.

“It was really, really cool to see someone like him, who, similar to me, grinded his way year in and year out, to get his opportunity,” Watkins said. “It’s phenomenal to see guys like that get their chances. It’s very heartwarming.”

Spenser Watkins, RHP
Prospect Ranking: Unranked
Debut date: July 2
Watkins threw one scoreless inning of relief work in the road game against the Angels. He did not record a strikeout, but needed just eight pitches to retire the three Angels batters he faced.

A former 30th-round draft pick by the Tigers in the 2014 MLB Draft, Watkins had a 3.58 ERA in 32 2/3 innings of work with Triple-A Norfolk this season. He has pitched 622 1/3 innings and has a career 3.86 ERA in seven seasons in the Minors since he was drafted out of Western Oregon University.

Alexander Wells, LHP
Prospect ranking: No. 17
Debut date: June 26
Wells became the third Australian-born player in Orioles history and the first since Damian Moss in 2003. The southpaw opened his career on a high note, throwing two innings of scoreless relief in the Orioles’ 12-4 loss to the Blue Jays.

Konner Wade, RHP
Prospect ranking: Unranked
Debut date: June 26
Wade had a rough go-around in his Major League debut, allowing six runs across 1 2/3 innings against the Blue Jays.

Mickey Jannis, RHP
Prospect ranking: Unranked
Debut date: June 23
A former 44th-round Draft pick, Jannis spent parts of eight seasons in the Minors, four in independent leagues and one in Australia before finally reaching the Majors at age 33 with the Orioles. He became the third-oldest rookie in O's history when he pitched the final 3 1/3 innings of Wednesday’s blowout loss to the Astros. He struck out his first hitter, Yordan Alvarez, but he ultimately allowed seven earned runs in his debut.

“The dedication he has to the game and to the grind, and for him to get an opportunity up here, it speaks volumes to his character and his perseverance,” Wednesday’s starter Thomas Eshelman said. “I was happy for him to get an opportunity.”

Tyler Nevin, 1B
Prospect ranking: No. 22
Debut date: May 29
Called up after just 17 Triple-A games to provide coverage for the injured Trey Mancini and Ryan Mountcastle, Nevin made history the minute he stepped on the field. He became the first Oriole ever to debut on his birthday, and only the 15th non-pitcher to do so since 1901. He then doubled and walked in his first two plate appearances off Dallas Keuchel. After the game, Nevin grew emotional speaking of relaying the news of his promotion to his dad, Yankees first base coach and former All-Star slugger Phil Nevin.

“We had talked about that call for the past couple years now, when it became more of a reality than just a dream," said Nevin. "Every time I even talk about it, I get choked up. He’s helped me so much, as a dad, as a mentor in this game. I always knew he would be the first call. It was special.”

Isaac Mattson, RHP
Prospect ranking: Unranked
Debut date: May 7
Rarely does a player hear the news of his MLB promotion from his future big league manager, but Mattson did. The right-hander was informed he was heading to the Majors by Hyde while on the treadmill last week -- such is life on the MLB taxi squad circa 2021. A few days later, Mattson was summoned to record the final two outs of Baltimore’s eventual 6-2 loss to the Red Sox. He allowed one run on one hit and one walk, in the process becoming the first prospect acquired by Mike Elias to appear in the Majors. Mattson was part of the four-player haul in the Dylan Bundy trade in December 2019.

Jay Flaa, RHP
Prospect ranking: Unranked
Debut date: April 27
A sixth-round Draft pick in 2015 who spent parts of the past seven years in the Minors, Flaa became only the 20th player from North Dakota to pitch in the big leagues when he debuted in mop-up duty for the Orioles against the Yankees. The righty logged 1 1/3 innings of scoreless relief, walking two in the ninth but striking out Aaron Judge to escape his debut unscathed.

“Escape artist,” Hyde said. “When he got behind in the count, I was a little concerned!”

Said Flaa: “It was pretty surreal being out there. There were a lot of emotions building up to that.”

Zac Lowther, LHP
Prospect ranking: No. 11, per MLB Pipeline
Debut date: April 25
The O's second-round pick in 2017, Lowther enjoyed success at every Minor League level before the pandemic, and he performed well at their alternate training site and big league Spring Training in 2021. His debut went smoothly, allowing one hit and striking out one over a scoreless ninth. Lowther retired the heart of the A's red-hot lineup, striking out All-Star third baseman Matt Chapman to end the game. His bullpen days may be numbered, as Lowther is a candidate to start later in the summer.

"Very cool moment for him and a nice way to break him into the big leagues," Hyde said. "I was pumped to watch him on the mound, and he didn't disappoint -- threw strikes, showed multiple pitches, didn't look nervous, though I'm sure he was."

Mac Sceroler, RHP
Prospect ranking: Unranked
Debut date: April 5
One of two Rule 5 Draft picks to win a bullpen job out of Spring Training, Sceroler made the jump from Class A Advanced (in the Reds' system) to the Orioles' Opening Day roster. He was then thrown right into the fire, inheriting a bases-loaded, one-out sixth-inning jam from Paul Fry in Baltimore's 7-0 April 5 loss to the Yankees. His first batter? Aaron Judge, whose solo homer off Jorge López in the fourth inning provided the Yankees a lead they wouldn't give back.

Sceroler was unfazed, freezing Judge with a 3-2 fastball en route to escaping the jam unscathed, and retiring his first seven big league hitters overall.

“I could finally breathe,” Sceroler said afterward. “I knew I was still in the game so I couldn’t relax too much, but I could take a few minutes to process what just happened, breathe and then get back to competing out there.”

By the end of the outing, he'd logged 2 2/3 scoreless innings of mop-up relief, striking out four and walking two. Meanwhile, unknown to Sceroler, the Orioles' broadcast Zoomed with his uncle, former O's pitcher and current analyst Ben McDonald. The righty made one more appearance before landing on the 10-day injured list April 13 with shoulder tendinitis.

“To be put in a situation like that, that’s what everyone wants to be put in just to prove themselves,” Sceroler said. “To show I can pitch and get the job done. It was comforting for me, to be put in that situation and to succeed.”

Ryan McKenna, OF
Prospect ranking: No. 15
Debut date: April 5
The Orioles' fourth-round Draft pick in 2015, McKenna advanced to Double-A Bowie in '19 and spent most of '20 at the alternate training site, earning some late-season taxi-squad duty. He was called up from the taxi squad in place of the injured Austin Hays to provide outfield depth, and immediately thrust into the starting lineup to spell everyday right fielder Anthony Santander. McKenna then experienced a quiet debut, going hitless with a walk in three plate appearances. He was summoned again when Santander landed on the injured list in April 21, going 3-for-15 with five runs scored in his first 13 big league games.

Tyler Wells, RHP
Prospect ranking: Unranked
Debut date: April 4
The 6-foot-8 Wells reached Double-A in the Twins' system in 2018, but he missed the next two years recovering from Tommy John surgery by the time the Orioles selected him, along with Sceroler, in the Rule 5 Draft. The righty earned a bullpen role out of Spring Training and debuted in the O's 11-3 win over Boston, pitching a scoreless ninth inning to close out their third victory of the season. Wells allowed one hit and walked one in his debut, but he stranded both baserunners, flashing two distinct breaking balls in the process. He allowed six earned runs in 7 2/3 innings across five appearances as of April 26.