Sinner secured a hard-fought 7-5, 6-7, 7-6 in over three hours of pure ball striking. It was the second win for the Italian in the green group and puts him in prime position to qualify for the last four at this year's ATP Finals where he is making his full tournament debut as a qualifying entrant.
Djokovic, meanwhile, suffered a big blow that could impede his chances of progressing beyond the group stage. It is worth noting that in his previous 15 trips to the year-end championships, the Serbian man was eliminated in the group phase on just four occasions.
So Djokovic's output is excellent and should certainly be favored to progress. There is a disclaimer heading to the final round-robin matches. Hubert Hurkacz will join in as an alternate to replace Stefanos Tsitsipas who suffered a back injury in his match against Rune and has pulled out from the event.
Because Rune was officially handed the win, it means Hurakcz can't qualify for the semifinal, but could still play a part in determining the fate of this group. The good news for Djokovic, he controls his own destiny. Djokovic is playing Hurkacz and Sinner and Rune will square off in the other match.
There are at least 16 different results that could happen in the final round-robin matches. Sinner has won two matches but is not assured to qualify. However, only two instances of the 16 will eliminate him, and one of them is if Djokovic and Rune secure straight-set wins.
Djokovic is the second favorite to qualify with at least nine of the 16 scenarios favoring him. If Sinner wins (irrespective of the score), Djokovic qualifies in second place even if he loses to Hurkacz.
Djokovic will be in big danger should Rune defeat Sinner in straight sets. That would mean he must beat Hurkacz in two sets to qualify together with the Dane. The only occasion Djokovic can top the group is based on the percentage of games won.
For this to happen, he'll need to take out the Pole in straight sets and hope Rune wins in three. You can check the full list of permutations for this group in the table below.