CNN  — 

Roger Federer said Novak Djokovic had a “truly exceptional” year, even as the world No. 1 fell short of winning a calendar grand slam at the US Open.

In New York this month, Djokovic was bidding to become the first man since Rod Laver in 1969 to win all four major tournaments in the same calendar year, but lost to Daniil Medvedev in the final.

Federer, who is recovering from knee surgery having last played at Wimbledon in July, added that he thinks achieving a calendar grand slam is still a possibility in the men’s game.