Novak Djokovic overcame a right wrist issue to defeat the Czech Republic's Jiri Lehecka 6-1, 6-7 (3), 6-1 and send Serbia through to the United Cup mixed team quarterfinals.?(More Tennis News)

The No. 1-ranked Djokovic and defending Australian Open champion was troubled by his wrist during practice on Tuesday morning, with the injury requiring intense treatment from his physio.

Djokovic was cleared to play his singles match and it was just as well after Wimbledon champion Marketa Vondrousova defeated Olga Danilovic 6-1, 3-6, 6-3 to give the Czechs a 1-0 lead.

The 24-time Grand Slam winner was on track for an easy victory against Lehecka after winning the first set and leading 3-1 in the second. But, with his wrist troubles growing as the match wore on, Djokovic started making a series of uncharacteristic unforced errors.

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Djokovic took a medical timeout after losing the second-set tiebreak, but he came out strongly with a double break in the third set to seal victory.

“I managed to play through,” Djokovic said of his injury. “It's not the first time or the last time, these things happen. You have to find a solution, and thankfully, I managed to finish the match and let's see what happens now.”

With Serbia's quarterfinal spot secured and Djokovic wanting to rest his wrist, the 36-year-old opted against playing in the mixed doubles.

If Serbia wins the mixed doubles, it will top Group C and meet Australia in the quarterfinals. That would also mean China would receive a quarterfinal berth as the best runner-up in Perth, eliminating the defending champion United States of America from further play.

If Serbia loses the mixed doubles, it will qualify for the quarterfinals as the best second-place team in Perth, and a quarterfinal Wednesday in Perth against Poland. China would then win the group and play Australia.

At Sydney in the first of two ties on Tuesday, Chile defeated Greece in the mixed doubles to claim a 2-1 win.

Stefanos Tsitsipas — runner-up at last year's Australian Open — was scheduled to face Chile's Nicolas Jarry in the men's singles match, but pulled out at the last minute with a back injury. He was replaced by 19-year-old Stefanos Sakellaridis, who lost to Jarry 6-3, 3-6, 7-5 to level the tie.

But, Greece won the mixed doubles in three sets to move into first place in its group ahead of Canada, which plays its final group game on Wednesday against Greece.

Maria Sakkari had given Greece a 1-0 lead with a 6-0, 6-1 victory over Chile's Daniela Seguel. Sakkari took just 26 minutes to wrap up the first set in the morning session at Sydney's Ken Rosewall Arena.

“I don't feel match sharp but I feel good,” Sakkari said. “I'm very happy to have given my team the first point and I have full belief in the team so I'm super excited for what's coming.”

Netherlands, 1-0, was scheduled to play Croatia, 0-1, in the late match in Sydney.