His attempts led to the player’s explosive row with the umpire and a code violation en route to defeat.
The cartoon has been condemned as racist by civil rights leaders, celebrities and fans.
She also said he treated her differently than male players during her loss to Naomi Osaka.
Djokovic, playing in his eighth final in New York and already the champion in 2011 and 2015, is now just three Slams behind Rafael Nadal and six back from the all-time record 20 held by Roger Federer
Williams was handed three code violations — and docked a point and then a game — in her 6-2, 6-4 loss to Naomi Osaka in the Flushing Meadows final
Naomi Osaka became the first Japanese to win a Grand Slam singles title on Saturday as her idol Serena Williams angrily imploded, calling the chair umpire in the US Open final "a thief".
Nadal won 40 percent of his first serves in the opener as he struggled with the high humidity on Arthur Ashe Stadium court, with Thiem becoming the first player to ‘bagel’ the Spaniard at Flushing Meadows since Andy Roddick 14 years ago.
Defending US Open champion Sloane Stephens was dumped out in the quarterfinals after losing 6-2 6-3 to Latvian 19th seed Anastasija Sevastova in sweltering conditions on Tuesday.
Millman advanced to a quarterfinal match-up against sixth seed Novak Djokovic
Novak Djokovic sweated his way to a 6-3 6-4 6-3 fourth round win over Joao Sousa as the heat returned to the US Open on Monday.