Isner has an extremely powerful and consistent serve, thanks in part to his 6-foot-10½-inch height which makes him the third-tallest player on tour behind Ivo Karlović and Reilly Opelka. Commentators have also praised his composure; in five consecutive third-set tiebreaker wins in Washington, D.C., he delivered huge serves when it mattered most. Isner also has a very powerful forehand, which he uses in tandem with his serve. Isner will often go for one-two points: a big serve followed up by a big forehand. He is also known to back up his serves with approaches to the net, though he does not strictly serve-and-volley. Isner's movement around the court is hampered by his body and he is hurt by players that move him around the court. Isner's fitness has improved considerably throughout the years, as he displayed during his win in the longest tennis match ever at Wimbledon against Nicolas Mahut.