Davis Cup: Djokovic's Serbia reaches quarterfinals

Serbia took an unassailable 3-0 lead over Russia after Nenad Zimonjic and Viktor Troicki clinched the doubles rubber.

Novak Djokovic celebrates Serbia's victory over Russia.

Serbia reached the Davis Cup quarterfinals on Saturday to set up a possible mouthwatering clash between Grand Slam heavyweights Novak Djokovic and Rafael Nadal for a semifinal spot.

Serbia, the 2010 champion, took an unassailable 3-0 lead over Russia in their World Group opener in Nis when 40-year-old Nenad Zimonjic and Viktor Troicki downed Andrey Kuznetsov and Konstantin Kravchuk 6-3, 7-6 (7/3), 6-7 (5/7), 6-4.

On Friday, Troicki beat Karen Khachanov 6-4, 6-7 (3/7), 6-3, 1-6, 7-6 (8/6) in the opening singles before Djokovic made it 2-0 when Daniil Medvedev retired with cramps in the fourth set allowing the 12-time major winner to claim a 3-6, 6-4, 6-1, 1-0 win.

Djokovic could face Nadal in the last eight in April should five-time champion Spain see off Croatia in Osijek in its season-opening tie which was locked at 1-1 overnight.

Nadal was sitting out the trip to Croatia after reaching the Australian Open final last weekend but would be certain to return to face a Djokovic-inspired Serbia.

Australia, the 28-time champion, completed a 3-0 drubbing of the Czech Republic in Melbourne when John Peers and Sam Groth breezed past Jiri Vesely and Jan Satral, 6-3, 6-2, 6-2.

Australia, captained by Lleyton Hewitt, will now face either the United States or Switzerland in the quarterfinals on April 7-9.

The United States was 2-0 ahead of a Switzerland side missing Roger Federer and Stan Wawrinka in Birmingham, Alabama, after Friday's singles.

World No. 20 Jack Sock got the United States off to a fast start, seeing off World No. 146 Marco Chiudinelli 6-4, 6-3, 6-1.

John Isner, ranked 23rd, had to work a little harder for a 4-6, 6-2, 6-2, 7-6 (7/1) victory over Henri Laaksonen, ranked 127th in the world.

"It would be a tough ask against the USA," admitted Hewitt of a potential clash with the record 32-time champion.

Nine-time champion France wrapped up a 3-0 victory against Japan after Wimbledon winners Pierre-Hugues Herbert and Nicolas Mahut brushed aside Yuichi Sugita and Yasutaka Uchiyama 6-3, 6-4, 6-4.

"We didn't play our greatest match but did what we had to do to win," said Mahut.

Japan, playing without World No. 5 Kei Nishikori, has yet to win a single set in three rubbers this weekend and will -- like all first-round losers -- now face a play-off later in the year to preserve its World Group status.

France will play either Canada of Britain for a place in the last eight.

It was locked 1-1 overnight in Ottawa after Dan Evans, his country's top player in the absence of World No. 1 Andy Murray, beat 17-year-old Denis Shapovalov 6-3, 6-3, 6-4.

Vasek Pospisil pulled Canada -- missing World No. 4 Milos Raonic -- level with a 6-4, 6-1, 7-6 (7/3) victory over Kyle Edmund.

Elsewhere on Saturday, defending champion Argentina was battling to stay in the tournament after slipping 2-0 down to Italy in Buenos Aires on Friday.

The winners of that tie will face either Germany or Belgium for a semifinal spot.

Belgium was 2-1 ahead in Frankfurt on Saturday after Ruben Bemelmans and Joris De Loore sealed a 6-3, 7-6 (7/4), 4-6, 4-6, 6-3 win over brothers Alexander and Mischa Zverev.

The reverse singles in all eight World Group ties take place on Sunday.