India, Aug. 26 -- Fans were left stunned while watching the opening round of the US Open, where Reilly Opelka was seen towering over opponent Carlos Alcaraz on Arthur Ashe. The 27-year-old American star caught fans by surprise as he posed for a photo with Alcaraz. The height difference between the two, as they stood beside each other, was incredible.

An old photo of the two standing side by side has also surfaced on social media.

Opelka is the joint-tallest player on the ATP Tour, standing at 6 feet, 11 inches tall. Alcaraz, on the other hand, is listed as being 6 feet tall.

The Laver Cup website describes Opelka as "the tallest man competing at Boston for Team World, one inch above fellow teammate John Isner and tied with Ivo Karlovic...