DETROIT -- Top pitching prospect Brusdar Graterol received his first Major League callup to headline Minnesota’s first wave of roster expansion on Sunday, and it didn’t take long for the Twins to get their first glimpse of the hard-throwing right-hander, who pitched a scoreless ninth inning in his Major League debut at Comerica Park.

The Twins will now continue to get a chance to see how the flamethrower's stuff plays at the highest level, with an outside chance that the youngster could be an intriguing wild card down the stretch. Minnesota's bullpen has looked increasingly solid -- following the acquisitions of Sergio Romo and Sam Dyson, as well as the quiet breakouts of Tyler Duffey and Trevor May.

Speedy outfielder Ian Miller also joined Graterol as new arrivals to the Twins' clubhouse, along with several familiar faces: fan-favorite utility man Willians Astudillo and pitchers Zack Littell, Devin Smeltzer and Kohl Stewart. LaMonte Wade Jr. was also activated off the 10-day injured list to provide needed outfield depth in the continued absence of both Byron Buxton and Marwin Gonzalez.

Kyle Gibson was also placed on the 10-day IL with ulcerative colitis, allowing the Twins to recall Lewis Thorpe, who had not yet spent 10 days in the Minors after he was optioned to Rochester on Aug. 26.

Because Graterol and Miller had not been on the 40-man roster, which previously stood at 39, the Twins needed to create room by placing pitcher Sean Poppen on the 60-day IL.

Littell should provide immediate depth in the Twins' bullpen, as the right-hander held opponents scoreless in 16 of his 17 relief appearances for Minnesota since he was made a full-time reliever. Stewart, Thorpe and Smeltzer could factor in as options in either the rotation or long relief.

They could soon be joined by Ryne Harper, who was optioned within the last 10 days and was unable to return. Sidearmer Trevor Hildenberger has also been lights-out out of the bullpen for Rochester since his return from injury.

With Graterol's promotion providing tangible evidence of the continued development of the Twins' top prospects this season, here's a quick look at several names to watch in the Twins' organization as the Minor League affiliates' seasons come to an end.

Arrival: Luis Arraez

Arraez was never ranked among the organization's top prospects and his breakout rookie campaign may have caught the greater baseball world by surprise, but the 22-year-old's success at the Major League level comes as no shock to the Twins. The infielder was a career .331 hitter in the Minors, with a superb eye at the plate and bat-to-ball ability. That has clearly transitioned well to the Majors.

Though Arraez first came up as a stopgap injury replacement, he quickly wrested control of regular playing time -- and eventually, an everyday starting role -- due to his consistently mature at-bats and line-drive ability. He owns a .332/.399/.427 line with three homers, 11 doubles and a triple in 68 games and has been worth 1.2 WAR, per FanGraphs.

Breakout: Jordan Balazovic

The Canadian right-hander was ranked by MLB Pipeline as the No. 29 prospect in the organization just last season. But he rocketed up to No. 4 this year, as he enjoyed another strong step in his development and was one of the Twins' representatives at the 2019 All-Star Futures Game.

The 20-year-old Balazovic dominated at Class A Cedar Rapids with 33 strikeouts and four walks in 20 2/3 innings before he was promoted to Class A Advanced Fort Myers, where he made an immediate splash by twirling seven perfect innings with 10 strikeouts in his debut. In all, he posted a 2.69 ERA with 129 strikeouts in 93 2/3 innings this season across the two levels.

Something to prove: Nick Gordon

This isn't a reflection of Gordon's performance, as he was likely in position to make his Major League debut earlier this season. Unfortunately, he had a strong campaign in Triple-A Rochester derailed by several injuries -- including gastrointestinal issues, an adductor strain and a lower leg contusion -- which combined to eat away more than two months of his sixth season in the Minor Leagues.

The adductor strain, in particular, came at an unfortunate time in mid-May. The Twins' roster was stretched to its limit due to injury, so Arraez was instead summoned to the Majors after only a minimal stint in Triple-A. Arraez forced his way into the Twins' immediate plans, which didn't leave Gordon much room to prove himself in the Twins' crowded infield situation.

Name to watch: Jhoan Duran

It says a lot about the current state of the top-level talent in the Twins' organization that several different names could go here. That list includes Alex Kirilloff, Trevor Larnach and Brent Rooker, all of whom could knock on the door of the Major Leagues next season.

But given the Twins' need in the starting rotation moving forward, it's worth highlighting Duran -- the organization's No. 9 prospect -- who has found a groove in Double-A Pensacola following a rough transition from Fort Myers. Duran, who headlined the return in last season's Eduardo Escobar trade, flashed a glimpse of his potential in an 11-strikeout, eight-inning scoreless appearance on Aug. 23. He has posted a 3.76 ERA with 136 strikeouts in 115 innings this season.