BALTIMORE -- In an effort to protect them from next month’s Rule 5 Draft, the Orioles added four of their top prospects to the 40-man roster on Wednesday, selecting the contracts of first baseman/outfielder Ryan Mountcastle, left-hander Keegan Akin, righty Dean Kremer and outfielder Ryan McKenna. By doing so, the

BALTIMORE -- In an effort to protect them from next month’s Rule 5 Draft, the Orioles added four of their top prospects to the 40-man roster on Wednesday, selecting the contracts of first baseman/outfielder Ryan Mountcastle , left-hander Keegan Akin , righty Dean Kremer and outfielder Ryan McKenna .

By doing so, the Orioles protected four of their seven Rule 5-eligible prospects from selection, while leaving No. 17 prospect righty Cody Sedlock, No. 29 prospect catcher Brett Cumberland and No. 30 prospect righty Gray Fenter unprotected. None have appeared above Double-A.

The deadline to shield prospects from Rule 5 selection was 8 p.m. ET on Wednesday. The Rule 5 Draft is scheduled for Dec. 12.

The Orioles’ 40-man roster now consists of 39 players.

The most interesting omission was Sedlock, the former first-round Draft pick who reached Double-A Bowie amid a rebound season in 2019. By leaving him exposed, the Orioles are betting no team sees the 24-year-old as a candidate to remain in the big leagues for an entire season just yet, despite his turnaround year. They were not as comfortable taking that risk with Mountcastle, Akin, Kremer or McKenna, all of whom could potentially contribute in the Majors in 2020.

Let’s take a look at the four prospects the Orioles protected on Wednesday, and what that decision means for their outlook next season and beyond:

1. 1B/OF Ryan Mountcastle

MLB Pipeline club ranking: No. 4, No. 64 MLB

2020 Opening Day Age: 23

2019 stats: .312/.344/.527, 25 homers, International League MVP at Triple-A Norfolk

MLB ETA: 2020

The highest-profile protected player was also the biggest no-brainer: Mountcastle, the Orioles’ reigning Minor League Player of the Year and top position player prospect not named Adley Rutschman. At this point, Mountcastle’s big league callup feels like a formality. It probably won’t come out of camp, but he probably won’t have to wait much longer, either. The Orioles, though, do want Mountcastle to clean up some plate discipline issues and grow more comfortable at first base and in the outfield before summoning him to Baltimore.

"I’m playing new positions, so getting a bunch of reps out there in the offseason will help,” Mountcastle said. “Being this close [to the big leagues], it makes you want to work a little bit harder and show the team I can perform.”

2. LHP Keegan Akin

MLB Pipeline club ranking: No. 11

2020 Opening Day Age: 24

2019 stats: 6-7, 4.73 ERA in 25 games (24 starts), 131 SO, 61 BB in 112 1/3 IP

MLB ETA: 2020

The organization’s Minor League Pitcher of the Year in 2018, Akin was clearly on a different development plan than many of the other hurlers who spent time at Triple-A last season. While the Orioles sent 18 others up and down, they kept Akin there the entire year, even as the Orioles’ big league rotation faced significant struggles and turnover. They simply thought his development was more important, challenging the left-hander to incorporate his slider more frequently to both sides of the plate and both bat sides.

"It was definitely a challenge. To do it at that level, playing against some guys who had 8-10 years of big league time already, that was something new for me -- to throw a 2-0 breaking ball or 2-0 changeup," Akin said. "Before, I would ride the fastball out. That was my best pitch. When we sat down in spring and looked at everything analytically, we made a plan. I realized you cant be a big league starter throwing 78 percent fastballs, which is what I did two years ago."

The results were something of a mixed bag: Akin paced the International League in strikeouts but also saw his walk rate spike. All told, his ERA jumped nearly a run and a half with his callup from Double-A. Still, with Akin a candidate to win a back-end rotation job out of Spring Training, protecting him was an easy call.

“He did some things he was never asked to do before,” director of pitching Chris Holt told MLB.com recently. “Overall, the work he did this year was very solid, continuing to round out his skillset as a pitcher. He was able to work on the things he will need to be able to do if he is going to compete in the big leagues.”

3. RHP Dean Kremer

MLB Pipeline club ranking: No. 8

2020 Opening Day Age: 24

2019 stats: 9-6, 3.72 ERA in 21 starts, 122 SO and 37 BB over 113 2/3 IP

MLB ETA: 2020

When it’s all said and done, Kremer might end up being the prize of the Manny Machado trade. He has performed consistently since arriving from the Dodgers in July 2018, and spent this past season turning heads across three levels of the Orioles’ system.

“I learned mainly that I have to be confident and sharp every time I go out there, no matter what I’m throwing and how I’m throwing,” Kremer said. “I need to show a consistent feel for all four pitches and the ability to get guys out efficiently. Always having a plan going after guys and portraying confidence, those are the biggest things for me.”

Kremer was slowed by an oblique strain early but hit his stride once he arrived at Double-A, pitching to a 2.98 ERA over 15 starts there. He struggled a bit in his first taste of Triple-A but shined again in the Arizona Fall League, posting a 2.37 ERA in six games (five starts). Barring injury, all signs point to Kremer beginning 2020 at Norfolk, where, like Akin last year, the Orioles will to try to resist the urge to rush him. But Kremer has a good chance to be in Baltimore by season’s end.

“He’s a very talented pitcher who really has a lot of feel for what he wants to do,” Holt said. “This year, he really made up for his slow start in the long haul. I’m super excited for him coming into 2020.”

4. OF Ryan McKenna

Pipeline club ranking: No. 13

2020 Opening Day Age: 23

2019 stats: .232/.321/.365, 9 HR, 25 SB at Double-A Bowie

MLB ETA: 2020

Protecting McKenna might have been a stretch -- he didn’t exactly light up Bowie offensively last year and has never appeared in Triple-A -- but utilizing some 40-man flexibility to do so probably won’t hurt the Orioles either. There is no guarantee McKenna remains on the roster past December, but if he does, it would certainly help his chances of breaking camp with a club that doesn’t currently have a clear answer for a fourth outfielder.

"It was a happy moment when you find out officially. When you go into the offseason you have it in the back of your mind, and my focus is to work as hard as I can,” McKenna said. “I thought there was definitely a chance. The Orioles organization has been very good to me and I was excited they were willing to take that chance on me.”

Joe Trezza covers the Orioles for MLB.com. Follow him on Twitter at @JoeTrezz.