The excitement of pitcher Jesús Luzardo joining the A's big-league squad in 2019 had to wait. But he more than made up for it.

Oakland's No. 1 prospect didn't make his major league debut until September after a strained left rotator cuff and a few minor setbacks, but now he finds himself among 2020 Rookie of the Year possibilities according to MLB Pipeline.

Luzardo's debut was everything A's fans wanted it to be, but it left everyone wanting more. It's a small sample size, but in six games, and 12 innings, he surrendered just five hits while accumulating 16 strikeouts and boasting a 1.50 ERA and 0.667 WHIP.

I know, I know -- there isn't a ton of data there, but it certainly got A's fans excited for what's to come next year. Luzardo should be in that starting rotation come Opening Day.

But he'll have a lot of competition if he wants to take home that Rookie of the Year honor, so the idea doesn't have us sold quite yet.

Jo Adell, the Angels' No. 1 prospect in 2019, is also another Rookie of the Year hopeful next season, and deservedly so. Despite missing a chunk of time during the start of the season due to injuries he suffered during spring training, he rose through the organization across all three affiliates.

Across those teams, Adell slashed .289/.359/.475 with 10 home runs. Yeah -- yeah, he got the boost in the PCL, but he's certainly one that will transition well. Plus the right-field spot could very well be open next season with Kole Calhoun hitting free agency.

Detroit Tigers top prospect Casey Mize is also on the rookie radar putting up gems like this last season with Double-A Eerie:

That’s a day for #Tigers Casey Mize and it’s a beaut:



▶️ 6.0 IP, 5 H, 1 R, 1 ER, 1 BB, 7 K - 88 pitches, 69% for strikes



Second 6 IP outing in his last three starts to allow 1 ER and first outing since June 7 with 7 or more strikeouts. — emilycwaldon (@EmilyCWaldon) August 7, 2019

[RELATED: A's excited to add Luzardo, A.J. Puk to 2020 rotation]

Waldon tells NBC Sports Bay Area that Mize's major league ETA is mid-to-late 2020, depending on health.

It's still the offseason so anything can happen, but Luzardo faces stiff competition for the 2020 AL Rookie of the Year.