Kyrgios is not the first player who struggled to quell emotions. McEnroe had many infamous outbursts. But he never quit competing, and that is what he and so many others find so perplexing about Kyrgios.
The mercurial Kyrgios put on a show for the sold-out crowd, fist-bumping with fans during the first set, smashing his racket in the second and mixing in tweeners, underhand serves and slick no-look volleys throughout.
Stefanos Tsitsipas overcame another shoe problem and an angry Benoit Paire on Friday to advance 7-5 6-0 and set up a semi-final against Australian firebrand Nick Kyrgios at the Citi Open in Washington.