MELBOURNE, Australia — Popular usage to the contrary, the definition of insanity is not doing the same thing over and over and expecting a different result.
Perfectly sane tennis players on losing streaks do it all the time, and so Andy Murray — of sound mind, if not always even temper — will do the same thing over again Sunday. He will walk into Rod Laver Arena looking a little disheveled and expecting to find a way to beat top-ranked Novak Djokovic in an Australian Open final.
Murray has lost all four of his past matches against Djokovic at the year's first Grand Slam, including three finals.
"Maybe it got to him, but it didn't break him," said Amelie Mauresmo, Murray's coach. "Now he comes back even stronger, each time believing that he can do it."
Believing it and achieving it are two different matters against Djokovic, the dominant player on the men's tour. But Murray, seeded second, earned a rematch by rallying to defeat the improved but still physically fragile Milos Raonic, 4-6, 7-5, 6-7 (4-7), 6-4, 6-2, on Friday in a matchup of stylistic contrasts that lasted 4 hours and 3 minutes.
Raonic saw his dream of a first Grand Slam singles final evaporate after he injured an adductor muscle in his right leg midway through the match.
For Murray to pull off the upset Sunday — against the odds, his accumulated fatigue and the weight of Djokovic's head-to-head advantage — will not be easy. Nor will it be quick. But Murray will not be surprised by the depth of the challenge.
"I have a very good shot on Sunday if I play my best tennis," he said. "I need to do it for long enough to have a chance. I'm aware of that.
"I don't think many people are expecting me to win. I have to just believe in myself, have a solid game plan and hopefully execute it and play well. But the previous disappointments, look, it's one tennis match. Doesn't matter what happened in the past, really. It's about what happens on Sunday."
Murray and Djokovic, born one week apart in 1987, go way back to their junior days in Europe. And they go way back in this tournament, where they once played doubles together, when both had longer hair and many fewer titles.
Their paths continue to converge, and their styles are still close enough to generate that mirror-image sensation when they face off along the baseline and cover it like the supreme athletes they remain at age 28.
Their numbers at the Australian Open are similar. Each is a great returner and has won 61 percent of the points against his opponents' second serves and about 33 percent against the first serve. Murray is putting 75 percent of returns in play, Djokovic 77 percent.
Yet there is an increasing disparity in the bottom line. Djokovic has soared into double digits in Grand Slam singles titles, with 10 to Murray's two.