NEW YORK — The U.S. Open final suddenly appeared to be slipping away from Novak Djokovic. He dropped three consecutive games. He was angered by a crowd roaring for his popular opponent, Juan Martin del Potro. He was, in short, out of sorts.

And then came Sunday’s pivotal game, a 20-minute, 22-point epic. Three times, del Potro was a point from breaking and earning the right to serve to make it a set apiece. Three times, Djokovic steeled himself. Eventually, he seized that game — and del Potro’s best chance to make a match of it.

A year after missing the U.S. Open because of an injured right elbow that would require surgery, Djokovic showed that he is unquestionably back at his best and back at the top of tennis. Djokovic collected his 14th Grand Slam title and second in a row by getting through every crucial moment for a 6-3, 7-6 (4), 6-3 victory over 2009 champion del Potro.

This was Djokovic’s third championship in New York, along with those in 2011 and 2015. Add in the trophies he has earned at six Australian Opens, one French Open and four Wimbledons, most recently in July, and the 31-year-old Serb pulled even with Pete Sampras for the third-most majors among men, trailing only Roger Federer’s 20 and Rafael Nadal’s 17.