Melvin Adon is known for his fastball. The Giants prospect has hit 102 mph, but another one of his pitches is earning praise in the Arizona Fall League.

Jim Callis, MLB.com’s lead draft and prospect writer, calls Adon’s slider the best in the Arizona Fall Stars Game. Adon will represent the Giants on the East squad in Saturday’s game featuring the Arizona Fall League's top prospects.

On Adon’s slider, Callis writes “his upper-80s slider has had more bite and consistency than in the past.” The big right-hander throws a slider that sits at 87 to 89 mph while consistently touching upper-90s with his fastball and surprising nobody when he reaches triple digits.

Here are two views of Adon striking out Nationals prospect Daniel Johnson with his slider.

In case you just didn’t believe it, here’s proof that #SFGiants RHP Melvin Adon has got a nasty slider. 🔥 pic.twitter.com/qi7eXgWUZu — Bridget (@bridgetmmulcahy) October 26, 2018

VICIOUS slider by Giants’ Melvin Adon, 87 mph after 100 mph gas to K Nats’ Daniel Johnson. Adon is 6’3” and built, explosive delivery. He can be a serious relief weapon in the Major Leagues pic.twitter.com/JEEbKxJhRq — Jacob Zweiback (@TheReelJZ) October 26, 2018

The sharp, sweeping breaking ball clearly can be a nasty strikeout pitch. What’s even more impressive is that the slider remains a work in progress. Former Giants reliever Aaron Fultz, who is Adon’s pitching coach in the AFL, said the prospect is working on a changeup and a slider, and both pitches have wowed him at times.

"One day I see his changeup where it’s like, ‘Wow,’ and one day I see his slider, and it’s the same thing,” Fultz said in a phone conversation with NBC Sports Bay Area.

Adon already had a naturally powerful arm when he arrived in the desert. The goal for the 24-year-old was to work on command and his secondary pitches. Both goals are being accomplished. In 9 2/3 innings out of the bullpen with the Scottsdale Scorpions, Adon has 19 strikeouts to two walks this fall. He has only allowed one earned run.

The 13th annual Fall Stars Game will start at 5 p.m. PT on MLB Network.