Djokovic secures United Cup quarterfinal spot

World No.1 Novak Djokovic overcame a wrist problem on Tuesday to defeat Jiri Lehecka in three sets, as Serbia beat the Czech Republic to set up a blockbuster United Cup quarterfinal with host Australia, reported Xinhua.

Serbia's comeback 2-1 victory powered them to the top of Group E in a result that means China will play top seeds Poland in an intriguing quarterfinal on Wednesday. Serbia will face Australia in the night session of the double header at RAC Arena.

Djokovic had been bothered by his right wrist during practice on Tuesday morning and he grimaced when the injury required medical treatment during his 6-1, 6-7 (3), 6-1 victory in the men's singles.

The niggle looms as a concern for Djokovic in his preparation for a record-extending 11th Australian Open title.

But having called for a medical timeout after losing the second set tiebreak, the 36-year-old Serb showed no ill effects as he ran away with the third set in 35 minutes.

"I managed to play through (the wrist injury)," Djokovic said, "It's not the first time or the last time, these things happen. You just have to manage.

"You have to find a solution and thankfully I managed to finish the match and let's see what happens now."

Djokovic was under pressure to keep Serbia's hopes alive after Wimbledon champion Marketa Vondrousova defeated Olga Danilovic 6-1, 3-6, 6-3.

But the 24-time Grand Slam champion dug deep having been in a tempestuous mood throughout, where he scolded himself on several occasions during an inconsistent performance.

Djokovic eventually rediscovered his top form as he embraced the support from the near capacity crowd at the 15,000-seat RAC Arena, most of whom were loudly cheering for Serbia.

In what was likely a precautionary measure, Djokovic did not play in the decisive mixed doubles with Serbia needing to win a set to prolong their tournament.

Serbia's pairing of Danilovic and Hamad Medjedovic were on the brink when Miriam Kolodziejova and Petr Nouza drew first blood before they rebounded to emerge victorious 4-6, 7-6 (2), 10-8.

In Sydney, Chile upset Greece with a 2-1 victory in Group B. They defied a rowdy contingent of Greek fans at Ken Rosewall Arena and were aided by No.6 Stefanos Tsitsipas withdrawing from his men's singles match against Chile's Nicolas Jarry due to a back injury.

The No.19 Jarry capitalised by defeating 19-year-old Stefanos Sakellaridis, but only after surviving a major scare to record a 6-3, 3-6, 7-5 victory. Sakellaridis, ranked 416, put up a gallant fight but fell short of a major upset as Chile levelled the tie.

Greece had earlier edged ahead after Maria Sakkari thrashed Daniela Seguel 6-0, 6-1 in the morning session.

Tsitsipas did play in the mixed doubles to partner Sakkari, but they fell to Seguel and Tomas Barrios Vera 6-7 (5), 6-3, 10-6.

Tsitsipas grimaced and clutched at his back late in the match in a worrying sign ahead of the Australian Open, where he finished runner-up to Djokovic last year.

In the later tie, Borna Coric gave Croatia the lead when he beat the Netherlands' Tallon Griekspoor 7-6 (4), 6-4 in the men's singles. Donna Vekic sealed the tie for Croatia with a 6-2, 3-6, 6-1 victory over Arantxa Rus.

But the mixed doubles decided who topped Group F and secured qualification for the final-eight. Norway emerged victorious as the Group F winner after Netherlands's 6-7(3), 6-3, 14-12 mixed doubles victory over Croatia.

In Sydney action on day six, France and Italy meet in Group D, while Greece plays Canada in Group B with quarterfinal spots up for grabs.