Novak Djokovic led Serbia into the quarter-finals of the United Cup on Tuesday despite struggling with a sore right wrist which required on-court treatment. 

The World No. 1 dropped a set in grinding past the Czech Republic’s Jiri Lehecka 6-1, 6-7 (3/7), 6-1 and required several visits from the trainer. He did not take part in the deciding mixed doubles, instead watching from the team bench as Olga Danilovic and Hamad Medjedovic defeated Czech pair Miriam Kolodziejova and Petr Nouza 4-6, 7-6 (7/2), 10-8.
 
It put Serbia into a last-eight clash with Australia on Wednesday. The result means that defending champions the United States are out, with one more day of play in Perth to go before the event shifts to its weekend finish in Sydney.