Slick playmaker Omar Abdulrahman can stake his claim for a big-money move to Europe when the UAE face Japan on Friday in an Asian Cup quarter-final which threatens to be a potential banana skin for the holders.

The mop-top Emirati is the heartbeat of Mahdi Ali's highly impressive UAE, who come up against a fast and powerful Japan side boasting the biggest names in Asian football.

Tennis greats Rafael Nadal and Novak Djokovic have acclaimed American Tim Smyczek's act of rare sportsmanship at a crucial time of his losing five-set thriller at the Australian Open.

With the score 30-0 deep in the fifth set a spectator yelled out loudly during Nadal's ball toss, which distracted the Spaniard and forced him to serve a fault.

Bayern Munich chairman Karl-Heinz Rummenigge on Wednesday defended the German champions' decision to play a friendly in Saudi Arabia amidst criticism surrounding the Arabic state's human rights record.

Bayern held their annual training camp in Qatar earlier this month before beating Saudi side Al-Hilal 4-1 in a one-off friendly in Riyadh on Saturday before flying home.

Spanish world number three Rafael Nadal survived a massive scare before winning a grueling five-setter with American qualifier Tim Smyczek at the Australian Open on Wednesday.

The 14-time Grand Slam champion prevailed 6-2, 3-6, 6-7 (2/7), 6-3, 7-5 in 4hr 12min and will now play unseeded Israeli Dudi Sela in the third round.

With the opening-match jitters behind them, all four teams in Group B of the African Cup of Nations are looking to set themselves apart from the rest.

Tunisia and Cape Verde, considered to be the strongest teams in the group, made sure that neither managed to gain an edge in the group standings with a 1-1 draw on Sunday.

Chinese real estate giant Wanda Group announced it bought a 20 percent stake in Spanish champion Atletico Madrid for 45 million euros ($52 million) on Wednesday.

"Wanda Group's capital contribution ... will allow Atletico Madrid to significantly shore up its balance sheet, as well as accelerate the growth of its brand globally," Atletico said in a statement on its website.

The Asian Cup knockout stage prepares for lift-off on Thursday with just two Arab countries left in the mix, continuing an alarming trend in recent tournaments.

Of the nine teams who travelled more than 7,000 miles (11,300 kilometres) to Australia, only Iraq and the United Arab Emirates reached the quarter-finals as the balance of power, which has swung irrevocably to the East, shows no sign of being corrected.

Second seed Maria Sharapova staged an epic comeback in the Melbourne Park heat on Wednesday after Russian qualifier Alexandra Panova pushed her to the brink of a humiliating second round exit.

The five-time Grand Slam champion saved two match points and had to draw on all her big-match experience to eventually down an opponent ranked number 150 in the world 6-1, 4-6, 7-5 after two hours 46 minutes.

Spain's Juan Jose Lobato Del Valle swooped in the last 50 meters to win the second stage of the Tour Down Under in the South Australian town of Stirling on Wednesday.

Lobato Del Valle came from 10th place in the closing stages to fly past South African Daryl Impey (Orica GreenEdge) at the end of the long uphill finish and win in 3hr 42min 24sec.

Novak Djokovic says his life is "completely fulfilled" as he bids to become the first player since Roger Federer to win a Grand Slam title after fatherhood.

The Serb world number one is gunning for his fifth Australian Open crown and eighth overall in the current major tournament in Melbourne, but has spoken glowingly of his new-found life as a husband and a father.