KANSAS CITY -- On the first day of expanded Major League rosters, the Orioles added outfielder Dwight Smith Jr. and relievers Tanner Scott and Branden Kline from Triple-A Norfolk.

Smith was in the Baltimore lineup on Sunday afternoon, going 0-for-4 as the Orioles lost the rubber game of the weekend series against Kansas City, 6-4, at Kauffman Stadium.

"I'm very excited and can't wait to compete and play this month out," Smith said prior to the game.

Smith was placed on the injured list on July 30 with a left calf strain. After being reinstated, he was optioned to Triple-A on Aug. 22.

Orioles manager Brandon Hyde declined to speculate on any possible callups after the Minor League season ends on Monday. Hyde said an overriding goal of the expanded roster period is to ensure that the Orioles have ample pitching options over the next four weeks.

"You want to be covered on the mound," Hyde said. "As we get later in the year and innings start piling up, you don't want to be [caught] short. We're looking to get deeper from a pitching standpoint."

Here’s a look who already has been called up and who else could be:

Arrival: Still just 24, right-handed pitcher Hunter Harvey stayed healthy this year, converted to a relief role and reached the Majors. The former first-round Draft pick immediately became one of the Orioles' best bullpen arms.

The excitement around Harvey is real. He has flashed his potential over his first handful of Major League appearances, showcasing excellent stuff. His fastball flirts with triple-digits, with a wipeout curve and a plus splitter to boot. He is enjoying his role, which is similar to the one his father Bryan had when he became an All-Star closer for the Angels and Marlins.

Now on the other side of the injuries that delayed his arrival, Harvey is entrenched with the Major League club and the Orioles are determined to keep him on the field.

Breakout: Something of a forgotten man in last summer's Manny Machado trade, infielder Rylan Bannon is the fastest-rising prospect in the Baltimore system. A little more than two years after the Dodgers made him an eighth-round Draft pick, the Xavier University product is knocking on the Major League door after his mid-August promotion to Norfolk. Bannon earned that upgrade and his Arizona Fall League invite with a productive stint at Double-A Bowie, hitting .255 with eight homers and 42 RBIs while playing mostly third base this season. Bannon also has experience at second. Scouts see the profile of a bat-first utility player at the next level. At the very least, Bannon already is likely to have earned an invite to 2020 Spring Training in Sarasota.

Something to prove: Outfielder Yusniel Diaz was the key return piece for the Orioles in the Machado deal, but his production has stagnated over parts of two seasons at Double-A Bowie, where this summer he hit .254 with 11 homers and a .782 OPS. Two stints on the injured list with leg injuries haven't helped, and Diaz is still just 22. But the Orioles were hoping for more growth from their No. 5 prospect in his first full year with the organization.

• Inbox: Will Mountcastle be up in September?

Name to watch: Infielder Ryan Mountcastle won the International League Most Valuable Player Award. The 22-year-old Mountcastle hit .309 with 25 homers, 35 doubles and 81 RBIs through 125 games with Norfolk. He's rated the No. 4 overall prospect in the Baltimore organization and the No. 68 overall prospect by MLB Pipeline.