John Isner praises and challenges rising Americans.
Naomi Osaka didn't need to hit a shot to reach the Miami Open fourth round for the first time.
The Canadian spoke briefly about his support for the PTPA.
The World No.3 won a round in singles and doubles before withdrawing.
Wearing new kicks, top seed stepped into Miami third round.
The co-founder of the PTPA taken to Twitter to praise Pospisil.
The former World No. 1, 34, announced the news on her social channels.
