Djokovic was expected to be in a better position ahead of the tournament but his early exit from the Italian Open has left Sinner with a strong chance to become the first Italian men’s world No. 1.
With Sinner and Alcaraz both missing the Italian Open due to injury, Djokovic had the chance to extend his lead at the top of the rankings.
Djokovic, who has spent a record 425 weeks as world No. 1, entered the ATP Masters event with 180 points to defend from making the quarter-finals last year, so could have gained points by reaching the semi-finals or final.
However, his shock third-round loss to Alejandro Tabilo has instead seen him lose points.