The 36-year-old, who holds a record 38 Masters titles, will aim to extend his unblemished 18-0 head-to-head facing the rejuvenated Gael Monfils.
The mercurial Frenchman is in inspired form, toppling Stefanos Tsitsipas en route to the Toronto Masters elite eight last week, and he's transferred that form over to Ohio.
The 36-year-old backed up a three-set seesaw with Cameron Norrie with a hot-shot laden 7-5, 6-4 passage past Toronto finalist Alex de Minaur.
"He's an amazing guy. Someone I truly respect and like a lot as a person," said Djokovic, hailing the Frenchman.
"He brings so much joy to the fans, so much entertainment. One of the most charismatic players that we've had in the past two decades on the Tour.
"It's great to see him back after several years of struggling with injuries. He's playing as good as ever. He's a year older than me. Everybody talks about my age, but what about him! He's doing amazing, so it's going to be a duel of the veterans tomorrow I guess."