Against John Isner, Reilly Opelka Stands Taller

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MELBOURNE, Australia — It started as a curiosity, believed to be the tallest match in tennis’s Grand Slam history.

And yet by the end of a nearly three-hour slugfest on the Australian Open’s opening day on Monday, fans here came away less impressed by all of the long-limbed height than by the guts of the surprising victor: the virtually unknown Reilly Opelka — 21, American, 7 feet tall in socks — who doled out an eye-popping upset by defeating his ninth-seeded compatriot John Isner, 33, who stands a looming 6-10.

Tennis players in the modern era trend taller than the players of yesteryear, even compared to those of 15 and 20 years ago. But not this much taller. In a…