The former World No.3 was seen working with Khachanov at D.C. and could end up joining the Russian's team long-term.
An injury-plagued season has altered Milos Raonic's Rogers Cup return.
Stefanos Tsitsipas cracked another ranking milestone while Nick Kyrgios is back in the Top 30.
Hall of Famers Kim Clijsters and Mats Wilander also scheduled to play.
The 15-year-old and 17-year-old teamed up for a title in D.C.
It was epic scened in the first ever meeting of Stefanos Tsitsipas and Nick Kyrgios at the Citi Open.
Benoit Paire called out Stefanos Tsitsipas on his shoe-breaking ways, and all heck broke loose at the Citi Open.
