World No 1 Novak Djokovic on Tuesday called for the Olympic Games to offer ranking points to help stem the flow of players turning their back on the showpiece event.

So far, 17th-ranked John Isner of the United States, Austrian 15th seed Dominic Thiem, world No 22 Bernard Tomic of Australia and Spanish veteran Feliciano Lopez, No 23 in the rankings, have all announced they are giving the Olympics in Rio in August a pass.

Isner said that as well as a packed summer schedule, the absence of ranking points was a major factor.