WATCH: Reilly Opelka advances to the main draw at the Miami Open

The 2019 season has been good to Reilly Opelka, as the American won the New York Open—his first career ATP title—and is now ranked No. 59 in the world.

Opelka has always been considered one of the more promising young Americans, and he is now really starting to come into his own.

Opelka's serve is his most dangerous weapon, which is the reason he draws a lot of comparisons to John Isner. And while his serve was already something that opponents were having trouble with last year, the 21-year-old insists that it's only getting better.

That's a scary proposition, and so is this: Opelka's baseline game is getting better, too. Despite his 6'11" size, the American moves quite well on the court. He's not going to win long rallies, but he's doing better at tracking balls down, and he knows his strengths. As Opelka continues to play more matches against stiff competition, he's only going to continue improving.

With Isner's title run in Miami last year, it's fair to wonder if Opelka's game makes him a threat to make a deep run this year. A lot of it will come down to match-ups, but the American will surely be a tough out for anyone.