Serb's new serve a talking point.
Young players can make the top, says Chang.
Opelka is NOT happy...
John Isner stunned in Atlanta.
Reilly Opelka won maiden title at New York Open.
Reilly Opelka gets the better of John Isner.
It was a day of upsets at the Delray Beach Open as Jack Sock, John Isner and Milos Raonic crashed out.