Five years ago, the Kansas City Royals selected Brandon Finnegan out of Texas Christian University in the first round. About three months later, the left-hander made his Major League Baseball debut against the New York Yankees. 

Finnegan went on to make seven postseason appearances for the Royals, including 2 1/3 innings in the marathon epic of a Wild Card game against the Oakland Athletics, on the team's way to the American League pennant. 

A prospect making that type of impact amid a title run is rare. More often, the call-ups are prospects on rebuilding teams who are gaining valuable experience for the 

As active rosters expand on Sept. 1 to 40 players for the final time in Major League Baseball history (a rule change effective next season will limit expansion to 28 players for the season's final month), here are some prospects to keep an eye on.

Jesus Luzardo, LHP, Oakland A's

A few months ago, Luzardo was a candidate for a spot in Oakland's rotation despite having never pitched in the majors. But the lefty suffered a strained rotator cuff in March that kept him on the shelf until June. He missed another month recovering from a lat strain. Luzardo has seen the mound every five days since Aug. 5, however, and ramped up to 84 pitches in 4 2/3 scoreless innings Sunday.  

Luzardo's big 2018 campaign established him as one of the top left-handed prospects in the game. The A's have already promoted fellow touted left-hander A.J. Puk to contribute out of the bullpen. If Luzardo isn't deemed ready to start in the majors, perhaps he could offer some assistance in relief as well. 

Gavin Lux, INF, Los Angeles Dodgers

Lux began playing like the first-rounder the Dodgers hoped for last season between High-A and Class AA. When he began 2019 with a solid start repeating Class AA, it was a sign to move him up. 

Class AAA is using the same "juiced ball" that has shepherded in a bounty of homers across the game, but nobody could have predicted what happened next. For nearly the last two months, Lux has been scalding hot and entered Thursday hitting .396/.480/.734 in 192 at-bats.

He's exclusively played shortstop this year, and Los Angeles has Corey Seager manning the position. But the Dodgers are not afraid to move players around the diamond to maximize lineup potential, and it's easy to see them getting creative to give Lux an opportunity. 

Deivi Garcia, RHP, New York Yankees

While Lux's peripheral statistics warrant a promotion, the same cannot be said for Garcia. Since being promoted to Class AAA in mid-July, Garcia's posted a 5.25 ERA with seven homers allowed in 36 innings.