Nadal, Federer play down Open feud

Federer said he was "completely cool" despite Nadal accusing him of not pushing hard enough for better players' rights, while the Spaniard regretted his comments made to media earlier.

"Things are fine between us, you know. I have no hard feelings towards him," Federer said.

"He's mentioned many times how he gets a bit tired and frustrated through the whole process, and I shared that with him. It's normal," he added.

"But for me, obviously nothing changes in terms of our relationship. I'm completely cool and relaxed about it. He seemed the same way -- or at least I hope so."

The short-lived row threatened to overshadow day one action at the year's first grand slam, where women's champion Kim Clijsters went through in straight sets alongside last year's runner-up, Li Na of China.

And as temperatures soared to 34 degrees Celsius (93 degrees Fahrenheit), Australian teen Bernard Tomic came from two sets down to beat Spain's Fernando Verdasco in the pick of the men's action.

Nadal admitted he probably should not have taken Federer to task so publicly. He had complained that the ATP Player Council president was not speaking out on issues such as more prize money and an easier schedule.

"These things can stay, must stay in the locker room," Nadal told journalists.

"I always had a fantastic relationship with Roger. I still have a fantastic relationship with Roger. That's what it should be, in my opinion. Don't create crazy histories about what I said yesterday, please.

"We can have different views about how the tour needs to work. That's all."

Nadal also revealed he suffered sudden and crippling knee pain on Sunday which threatened to end his tournament, before recovering after intensive medical attention.

The 2009 champion, who has had injury problems on his past two visits to Melbourne Park, put the emergency behind him to beat American Alex Kuznetsov 6-4, 6-1, 6-1.

Federer had an easy 7-5, 6-2, 6-2 workout against Russia's Alexander Kudryavtsev, a player so obscure that he had to scour the Internet in an effort to learn about his game.

"I heard a few things about him on the Internet and I knew what to expect although I didn't know his favourite shots or weaknesses," he said.

Nineteen-year-old Tomic had the performance of the day when he came from two sets behind to win 4-6, 6-7 (3/7), 6-4, 6-2, 7-5 against Verdasco, who draped himself in ice packs and battled nausea in the hot afternoon sun.

"If it was someone else, I think they would have thrown in the towel," Tomic said. "I don't know how I found the energy today."

Former US Open champion Juan Martin del Potro saw off Adrian Mannarino in four sets, and China's French Open champion Li also suffered in the heat during her 6-3, 6-1 win over Kazakhstan's Ksenia Pervak.

Defending champion Kim Clijsters raced into the second round and third seed Victoria Azarenka maintained her winning start to 2012 with a comprehensive 6-1, 6-0 demolition of Britain's Heather Watson.

Top seed Caroline Wozniacki began her latest bid for a maiden grand slam with an easy victory over Australia's Anastasia Rodionova, and third seed Victoria Azarenka stayed unbeaten in 2012 by demolishing Briton Heather Watson.

In the men's draw Czech seventh seed Tomas Berdych accounted for Albert Ramos in four sets, Stanislas Wawrinka beat Frenchman Benoit Paire in straight sets and American eighth seed Mardy Fish downed Luxembourg's Gilles Muller.

Spanish 10th seed Nicolas Almagro knocked out Poland's Lukasz Kubot, 1-6, 7-5, 6-3, 7-5 and Germany's Tommy Haas ousted American qualifier Denis Kudla in four sets.

David Nalbandian went through when Finland's Jarkko Nieminen, who won last week's Sydney International after coming through qualifying, retired in the second set with strained stomach muscles.