NEW YORK (Reuters) -World number one Novak Djokovic is a match away from one of the highest achievements across sports, with a calendar Grand Slam on the line after he overcame German Alexander Zverev 4-6 6-2 6-4 4-6 6-2 in the U.S. Open semi-final Friday.

Djokovic moved within one win of reaching a men’s record 21 Grand Slam titles and avenged his loss to Zverev at the Tokyo Olympics in front of a roaring crowd inside Arthur Ashe Stadium, with Rod Laver sitting in the front row, 52 years after he achieved the feat, the last man to do so.