World No. 1 Novak Djokovic apologized to the Belgrade crowd after he ran out of gas in the third set of the final versus Andrey Rublev. Djokovic, seeded at No. 1, was hoping to win his second Belgrade title and also his first title of the year. Unfortunately for Djokovic and the Belgrade crowd, Rublev delivered a great performance to upset the Serb 6-2 6-7 (4) 6-0. It was Djokovic’s fourth third-set match at the tournament. Earlier in the tournament, Djokovic needed three sets to beat Laslo Djere, Miomir Kecmanovic and Karen Khachanov, respectively. Djokovic was down by a set in …