"I think it's sometimes more of an emotional, mental thing," said Coco Gauff of her serving struggles.
The pair of legends past and present met up on Saturday at the Open.
Karolina Muchova has not dropped a set returning to the US Open fourth round.
"He's a very tricky player. Probably has one of the best hands on tour," Alexei Popyrin said of fourth-round opponent Frances Tiafoe.
Grand Slam king Novak Djokovic suffered his earliest US Open exit since 2006.
A candid Novak Djokovic says his earliest US Open exit since 2006 came down to a couple of key issues.
The American talked about his resurgence, and return, after his win over Ben Shelton
