The No. 6 seed won the 2:49 match 6-3, 6-4, 6-4. Djokovic looked exhausted after a 60-minute first set, but was given a brief break as Millman requested a change of clothes due to the extreme humidity.
Millman went up 1-0 and eventually held a 4-3 edge in the second set, until Djokovic came roaring back. The Serbian tied the set at 4-4 before winning consecutive points to take the set. Millman also went up 1-0 in the final set, before Djokovic earned a 3-1 edge. Millman fought back to take a 4-3 lead before Djokovic finished him off by winning the final two points of the game. Djokovic will appear in his 33rd major semifinal after dispatching of Millman.
No. 7 Marin Cilic also beat No. 21 Kei Nishikori in five sets to advance to the semifinals. No. 14 Madison Keys beat No. 30. Carla Suarez Navarro in straight sets 6-4, 6-3 on the women's singles circuit. No. 20 Naomi Osaka also advanced to the semifinals by beating Lesia Tsurenko in straight sets 6-1, 6-1.
No. 17 Serena Williams takes on No. 19 Anastasija Sevastova in the semifinals at 7 p.m. on Thursday in New York. Keys faces Osaka at 8:15 p.m. in the other semifinal clash.