Djokovic, who was forced to skip last year's tournament due to an elbow injury and returned to the tour this year after surgery, said he was thrilled to be back on the big stage.
There were other issues for him, too, including in the third set when, ahead by a break, he was called by the chair umpire for allowing the 25-second serve clock, making its Grand Slam debut at this tournament, run out on back-to-back points. The No. 3 Argentine advanced after defending champion Rafael Nadal retired from Friday's other semifinal with a knee injury.
Novak Djokovic, of Serbia, hits a forehand to John Millman, of Australia, during the quarterfinals of the U.S. Open tennis tournament September 5, 2018, in NY.
Perhaps it's because del Potro was sandbagging.
Humanitarian notions that five-setters are reducing the best players to physical wrecks is somewhat diluted by the presence in Sunday's US Open final of Novak Djokovic and Juan Martín del Potro, who have experienced more than their share of physical and spiritual hurt in long, garlanded careers.
When he swept to the 2009 title in NY, he was just 20 years old and expected to establish himself as a permanent rival to Djokovic, Federer and Nadal.
Both players missed the 2017 U.S. Open with injuries, but were on the cusp of returning to the finals. Djokovic, another player whose recent injury cost him time at the top of the tennis pyramid, won Wimbledon this year and is rounding into his elite form again.
Nadal attempted to hold his serve down 2-5 in the second but was broken to drop the set. Then I think it was a little bit better.
A quarter-final defeat at Roland Garros, where he had completed the career Grand Slam in 2016, left him in deep despair, threatening even to skip Wimbledon. You could imagine very hard for me to say good-bye before the match finish.
"It means a lot to me", del Potro said. A straight-sets win is not out of the question for the two-time champion, whose incredible consistency at the US Open is set to continue.
"I can not compare the knee with other times as the pain is always very similar".
"I feel like he is on his way back", Williams said.
As everybody knows, this is my favorite tournament since I'm kid. We all knew that he had a capacity and a quality to get to the point where he is at the moment.
But Nadal was unable to take advantage and immediately after the time-out, with the 32-year-old struggling to cover the court, Del Potro broke again. That's where he got, I feel like, a great confidence boost. "I am focused on trying to make that happen".