Reilly Opelka

Reilly Opelka is tied with Ivo Karlović as the tallest player in ATP history at 6 feet 11 inches, and he has spent his career bending that frame into one of the most untouchable serves the sport carries. Born in St. Joseph, Michigan and raised in Palm Coast, Florida, the American came up through the USTA's Boca Raton training center and turned pro in 2015 — the same year he won the boys' singles title at Wimbledon, beating Mikael Ymer in the final after getting past a young Taylor Fritz in the draw.

The game is the delivery, full stop. From that height Opelka generates first serves north of 140 mph and a kick second serve that few opponents can attack, which turns his matches into breaker-laden holding contests where a single return point can decide a set. He is a career leader in tiebreaks played and aces hit per match, and he leans on a flat, heavy forehand to end the rare rallies that get past his serve. The trade-off is mobility — he is exposed on the stretch and in long baseline exchanges, which is why clay has always been his least productive surface.

The breakthrough years brought four ATP titles and a run to a career-high ranking of No. 17 in 2022, built on hardcourt results and deep weeks at events like Indian Wells and the Canadian Open, where his serve scales best. He's a familiar second-week threat to bigger names — the kind of floater seeds dread drawing — and his outspoken, contrarian streak off court has made him one of the tour's more quotable personalities.

A series of wrist and hip problems cost Opelka long stretches and dropped him out of the rankings, and at No. 86 he is still climbing back toward the top tier his serve has always promised.