Andy Murray has attributed his success this season to his improved fitness, as evidenced by his Sony Ericsson triumph.

Andy Murray became the first Briton to win the Sony Ericsson Open with a straight sets win against Novak Djokovic. The 21-year-old was in superb form during the Miami tournament, dropping just two sets on the way to the final which he convincingly won 6-2 7-5 despite the blistering hot conditions.

Whereas the heat may have slowed Murray in years gone by, the Scot looked unfazed as he secured a win that moves him to the brink of passing Djokovic into third place in the world rankings.

Already many pundits believe Murray is worthy of that status, even if the rankings don't suggest it, and his recent form would back such claims.

Since losing to Rafael Nadal in the quarter-finals at Wimbledon last year Murray has returned a win-loss record of 57-7 - the best mark on the ATP tour ahead of the world number one Nadal's 50-7.

And Murray believes a key reason for his all-conquering form can be simply be put down to the fact he is physically better prepared.

"(It) just gives you more confidence going into the matches knowing you're in good shape," he said.

"I think just mentally it makes a difference. Even if you're struggling, you know your opponent is going to be feeling the same, as well.

"Whereas before sometimes you could get tired and look over at the other side and the opponent seems fine. A match like today, there's obviously points...I mean, it was hot out there.

"A few long rallies and stuff I would be a little bit out of breath. I could look down the court and see him struggling, as well."

Djokovic agreed with Murray's self assessment, admitting the ability of his fellow 21-year-old to retrieve more balls has made him a more dangerous player.

"I think physically he's moving much better all over the court," the Serbian said.

"The balls he wasn't getting before he is now. The switch of defensive to offensive tennis in the points - he is really good, one of the best in the world.

"I think that makes him a much better player than he used to be."

With the Sony Ericsson Open the last in the hard-court season, Murray will now turn his attention to trying to improve his performances on clay ahead of the French Open.

Murray admits he still has some way to make up to compete with the likes of Nadal, Djokovic and Roger Federer on the surface if he wants to break into the top three.

"The clay-court season will be very important for me now," Murray said.

"On hard courts, my game is up there with the others but on clay it hasn't been the same. If you take the results on it out of the equation, I'm very close to Roger and just behind Rafa, so I need to improve."