World No. 1 Novak Djokovic said he was “not sure” about his fitness for the US Open after pulling out of the Tokyo Olympics mixed doubles bronze medal match with a shoulder injury on Saturday.

The Serb, 34, could become the first man to complete a calendar Grand Slam since Rod Laver in 1969 when the US Open gets under way on August 30.
The withdrawal in Tokyo came after the 20-time major champion lost his cool on his way to a surprise 6-4, 6-7 (6/8), 6-3 defeat against Pablo Carreno Busta in the Olympics singles bronze-medal match.