"I thought about doing this t-shirt a few days ago," said Djokovic. "I didn't share it with anybody. Kobe was a close friend of mine, we chatted a lot, about the winner's mentality."
The 36-year-old Serb becomes the oldest U.S. Open men’s winner in the Open Era and the first to win three Grand Slam events in a season for the fourth time.
Gauff, 19, produced a gutsy performance on the Arthur Ashe Stadium court to win 2-6, 6-3, 6-2 in 2hr 6min to complete a fairytale transformation in her season's fortunes.
Novak Djokovic earned himself another shot at a record-equalling 24th Grand Slam title after beating unseeded American Ben Shelton in straight sets on Friday to advance to his 10th US Open final.
Daniil Medvedev upset defending champion Carlos Alcaraz in an enthralling semi-final duel to reach the US Open final on Friday.
Aryna Sabalenka fought back from the brink of defeat to overcome American 17th seed Madison Keys in a third-set tie-break and line up a US Open final against home favourite Coco Gauff.
The US Open was plunged into chaos on Thursday after environmental activists disrupted play, forcing a 49-minute stoppage as the tennis showpiece became the latest high-profile sporting event to be targeted by protesters.
American teenager Coco Gauff shrugged off a 50-minute stoppage caused by climate protesters to power into the US Open final on Thursday with a straight sets defeat of Karolina Muchova.
Defending champion Alcaraz moved to within one win of a potential dream final with Novak Djokovic with an emphatic straight sets victory over German 12th Alexander Zverev.
New York has been sweltering in a heatwave this week, with high humidity and temperatures at Flushing Meadows on Wednesday hitting 35 degrees Celsius (95 Fahrenheit)