(SP)SERBIA-BELGRADE-TENNIS-NOVAK DJOKOVIC (201023) -- BELGRADE, Oct. 23, 2020 (Xinhua) -- Serbian tennis player Novak Djokovic speaks during an improvised press conference after his training session in Belgrade, Serbia on Oct. 22, 2020. (Photo by Predrag Milosavljevic/Xinhua) Predrag Milosavljevic Photo: XINHUA/PIXSELL
(SP)SERBIA-BELGRADE-TENNIS-NOVAK DJOKOVIC (201023) -- BELGRADE, Oct. 23, 2020 (Xinhua) -- Serbian tennis player Novak Djokovic speaks during an improvised press conference after his training session in Belgrade, Serbia on Oct. 22, 2020. (Photo by Predrag Milosavljevic/Xinhua) Predrag Milosavljevic Photo: XINHUA/PIXSELL
(SP)SERBIA-BELGRADE-TENNIS-NOVAK DJOKOVIC (201023) -- BELGRADE, Oct. 23, 2020 (Xinhua) -- Serbian tennis player Novak Djokovic returns the ball during an open training session in Belgrade, Serbia on Oct. 22, 2020. (Photo by Predrag Milosavljevic/Xinhua) Predrag Milosavljevic Photo: XINHUA/PIXSELL
(SP)SERBIA-BELGRADE-TENNIS-NOVAK DJOKOVIC (201023) -- BELGRADE, Oct. 23, 2020 (Xinhua) -- Serbian tennis player Novak Djokovic (2nd L) speaks during an improvised press conference after his training session in Belgrade, Serbia on Oct. 22, 2020. (Photo by Predrag Milosavljevic/Xinhua) Predrag Milosavljevic Photo: XINHUA/PIXSELL
(SP)SERBIA-BELGRADE-TENNIS-NOVAK DJOKOVIC (201023) -- BELGRADE, Oct. 23, 2020 (Xinhua) -- Serbian tennis player Novak Djokovic speaks during an improvised press conference after his training session in Belgrade, Serbia on Oct. 22, 2020. (Photo by Predrag Milosavljevic/Xinhua) Predrag Milosavljevic Photo: XINHUA/PIXSELL