BALTIMORE—Taking advantage of a rule that will allow players on 40-man rosters to play in the major leagues and Arizona Fall League, the Orioles decided to promote outfielder Austin Hays for the final three weeks of the season.

General manager Mike Elias said that Major League Baseball and the Players Association came to an agreement this week on the rule. The AFL begins play this year on September 18. In previous years, it began after the regular season ended.

Hays, who will finish the season with the Orioles and then report to the Surprise Saguaros, will get at-bats that he missed because of a second straight injury-marred season.

Two years ago, Hays had an outstanding season at High-A Frederick and Double-A Bowie and moved up to the major leagues barely a year after he was drafted in June 2016.

Hays, who is 24, played 20 games with the Orioles in 2017, hitting a home run with eight RBIs and a .217 average.

“I hadn’t failed at all the last time I came up here,” Hays said.

“Everything went about as well as something could possibly go to start your career. Since then, it’s been about as bad dealing with injuries and failures. Half my games have been rehab games playing at levels that I thought I was done with. I’ve grown a lot, mentally, physically, my patience with myself, not trying to do too much, just trying to compete at a high level when I’m on the field.”

In 2018, Hays had a left ankle injury that eventually required surgery in September. This year, he sprained a thumb sliding headfirst into second base just after he didn’t make the Orioles out of spring training; later, was slowed by a hamstring injury.

Hays has played a combined 162 games in the minors the last two seasons, mostly in center field.

“I’m definitely more comfortable than I have been the last few years,” Hays said. “More games, more reps, more reads, more throws, angles, all that kind of thing. I’m very comfortable. I love it.”

The Orioles have 36 players and, with the additions of Hays, Mark Trumbo and Mason Williams, playing time for them and Dwight Smith Jr., DJ Stewart and Stevie Wilkerson might be a challenge for manager Brandon Hyde.

Anthony Santander will continue to play the outfield regularly. Trey Mancini will play first base and right field.

“The other guys I’m going to rotate and shuffle around,” Hyde said. “They’ll all get at-bats and give them long looks.”

Hays will be the 58^th Oriole to play for the team, and Hyde is beginning to see the future come into focus.

“It’s exciting to bring up younger players that have tools,” he said. “You can kind of get a glimpse at what it’s going to look like a couple of years from now.”

Hyde plans to play Hays in center field.

“I thought he played really well in center field in spring training,” Hyde said. “I like the energy he plays with.”

Mountcastle, Mullins and Akin: Three prominent prospects who weren’t added to the Orioles when the roster expanded to 40 this week were Norfolk’s Ryan Mountcastle and Keegan Akin, and Bowie’s Cedric Mullins, who hit for the cycle Saturday.

Fans were particularly eager to see the 22-year-old Mountcastle, who was named the International League’s Most Valuable Player.

“We still think he is developing,” Elias said. “We’re thrilled with the season he had offensively. If there’s something to nitpick there it’s his plate discipline, and he knows that. He’s not a big walker, and he’s still striking out a little bit. But that’s not to put a damper on what he’s done at age 22 in Triple-A.”

Mountcastle played first base and left field for the first time as a professional, and Elias implied that he might not begin the 2020 season with the Orioles.

“He’s also still doing some work on his defense and, long story short, I think he’s going to spend some more time in the minor leagues as a result of those two things,” Elias said. “But also at the major league level we’ve got quite a few players here that we want to provide these at-bats to in September. A guy like [Renato] Nunez or even a Mason Williams and a Santander.

“There’s just a lot of people here that we need to continue evaluating both in terms of our short- and long-term plans. So just didn’t see the avenue to call up Ryan at this time. But he’s going to be here, and he’s going to be a big part of our future at some point.”

Akin was 6-7 with a 4.73 ERA in 25 games. Elias was disappointed that the left-hander walked nearly five batters per nine innings.

“These guys, they’re big prospects,” Elias said. “If need be, could they come to the big leagues? Yeah. They’re not fully finished with their development really for the same reasons, and it’s walk rate in a lot of cases.

“… But his strikeout numbers are great. He had a nice full season, got [112] innings under his belt, and he will be in a very strong position to compete for a rotation spot [next] year, and I fully expect him to be in the major leagues with us next year.

“Again, thrilled to have him, but part of the rebuilding process that we’re going through in its early stages is we also try to bring in talent from the major league level outside — the guys that we have here, waiver claims, and give them some rope and try to find some diamonds in the rough that way. These guys are coming, and they’re a big part of our future.”

Mullins started the season with the Orioles, but after hitting .094 (6-for-64) in 22 games, he was sent to Norfolk, and after hitting .205  was demoted to Bowie, where he’s playing in the Eastern League playoffs.

He’s hit .271 in 51 games with the Baysox.

“I don’t think we’re going to be calling Cedric up,” Elias said. “I talked to him the other night in Bowie. It’s been a lost season for him in a lot of ways, and the fact that he has ended up back in Bowie is not something I ever would’ve dreamt or would’ve wanted to see, and I don’t think he did, either.

“We do think that he might benefit from making some mechanical changes and some very focused mechanical work. He’s got a real good approach. He’s got a lot of ability. He’s still really young, and he’s still a heck of a centerfielder, so we’re going to put together a program for him in the offseason to work on his swing. But at this time, with the number of outfielders who we have, I’m not anticipating that, but certainly if something changes, it’s a possibility.”