Champions invariably win when they are playing their best, but what makes them champions is that when the chips are down, they find a way through when there does not appear to be any available.

Rafael Nadal, Maria Sharapova and, to a lesser extent, Roger Federer, dug deep into their reserves today to take their places in the third round at the Australian Open.

Federer shrugged off a nasty blister on his right hand and a weird pain on the end of one of his fingers - that may or may not have been a bee sting - to get past Italy's Simone Bolelli in four sets.

But the real drama involved two of the sport's biggest fighters as Sharapova flirted with disaster and then Nadal overcame dizziness and cramps to survive a five-set epic.

Having made more than 50 unforced errors, Sharapova was staring defeat in the face when her fellow Russian Alexandra Panova held two match points at 5-4 in the final set.

But as she has done so many times, Sharapova held firm, saved them both and then went on to claim a 6-1, 4-6, 7-5 victory, all the more impressive given that she trailed 4-1 and 40-15 in the final set.

Her boyfriend, Bulgaria's Grigor Dimitrov, said she was "by far the greatest fighter ever", while Sharapova herself said she needed to dig herself out of a rut.

"My thought process throughout the match to that point was pretty negative," she said. "I think I was dwelling too much on my mistakes.

"I just really tried to take it one point at a time, think positively, and change my thought process a little bit. When other things are not working, maybe the mental side of things will help you out. I think that's what did it."

Nadal needed the doctor, a pill and his unbelievable will to win to deny American world No 112 Tim Smyczek what would have been the biggest win of his life.

The Spaniard, who missed much of the second half of 2014 with wrist and back injuries, as well as appendicitis, complained of dizziness after the second set but recovered to scramble through 6-2, 3-6, 6-7, 6-3, 7-5.

Smyczek produced the performance of his life and a generous piece of sportsmanship in the final game when he offered Nadal a first serve, after a spectator had shouted out just before the 14-times grand slam champion served.

When Nadal finally put a forehand away to win on his fourth match point, he fell to the court, the emotions coming out.

"It was a very tough night for me," Nadal said. "I don't know what was going on but I was having cramps around the body, in different places, which says that I was not in my perfect shape."

Dimitrov moved within one win of a clash with Andy Murray after he beat Lukas Lacko of Poland in four sets while Australia's good tournament continued with Nick Kyrgios, Bernard Tomic and Sam Groth all advanced, alongside Tomas Berdych and Eugenie Bouchard.