US Open: Novak Djokovic fights back to beat Matteo Berrettini in four sets, enters semis

Novak Djokovic again fought back from a set down to beat Matteo Berrettini 5-7 6-2 6-2 6-3 and move into the U.S. Open semi-finals on Wednesday, the Serb now just two wins away from a 21st major that would complete a calendar-year Grand Slam.

Djokovic, who also lost the opening set in his previous two matches, and Berrettini have met only three times but two were this year when the stakes were at their highest -- the Wimbledon final and French Open quarters -- with the world number one winning both times in four sets.

The 25-year-old Italian had a third shot at derailing Djokovic`s Grand Slam plans on Wednesday but once again could not seize his chance, converting just one of five break opportunities, that coming in the first set.

Djokovic takes another step up in class in the next round, where he faces fourth seed Alexander Zverev, the player who last month ended his bid for a `Golden Slam` by beating him in the Tokyo Olympics semi-finals.

Zverev arrives at the final four as the hottest player in men`s tennis, advancing with a 7-6 (6) 6-3 6-4 win over unseeded South African Lloyd Harris to extend his winning run to 16 matches.