More than one way to play - Monfils

New York - Gael Monfils insisted his bizarre 'rope-a-dope' tactics in his US Open semi-final defeat to Novak Djokovic were deliberate as the eccentric Frenchman blasted accusations of deliberately not trying.

Defending champion and world number one Djokovic triumphed 6-3, 6-2, 3-6, 6-2 to reach his 21st Grand Slam final, where he will face either Stan Wawrinka or Kei Nishikori for his third major of 2016 and the 13th of his career.

But the semi-final was clouded by controversy when 30-year-old Monfils appeared to stop competing in the first set, standing inside the baseline, airily slicing first serves back to Djokovic.

The French player had lost all 12 career meetings with Djokovic prior to Friday and after he slipped 5-0 down in the first set, he slammed on the brakes in a desperate effort to turn the tide.

It worked briefly as he retrieved three games but after dropping the second set, where he was broken twice more and was roundly booed, he reverted to a more traditional approach.

He restored his reputation in the last two sets but he still faced claims he was 'tanking' and hit back at American legend John McEnroe who said he had been "unprofessional".

"I tried to get inside Novak's head," said Monfils. "It was a very quick 5-0. I had to change a little bit. I think it worked. There's not only one way to play tennis. When the guy is hitting clean and you're not serving good, you just show him. You stand in the middle of the court.

"He starts to double fault a little bit. Then you give him a very slow ball. And then he comes to the net. I pass him. Was great strategy.

"When I tried to play 'original' tennis, he kills me."

Monfils was furious that he had been branded as unprofessional by McEnroe who was commentating for American television.

He believes he was right to adapt his tactics and that it illustrated just what a competitive player he remains despite many in the sport viewing him as an unfulfilled talent.

Before Friday, his only other semi-final at a major was at Roland Garros in 2008.

In 2014 at the US Open, he threw away a two sets to love lead and two match points to lose to Roger Federer in the quarter-finals.

"Fuck, yes, I'm competing," raged Monfils. "Everyone is not doing this because of all the questions they gonna receive that it's not natural.

"The first question is you're not competing. The guy is too good. To change is guts, I show you that I play non-academic way."

Djokovic admitted Monfils's bizarre approach had unsettled him and that he had been foolish to get drawn into the trap.

"I thought at times that he was maybe behaving a little bit, for some terms and judgements, unacceptable but I guess that was part of his tactics," said the 2011 and 2015 champion.

"If he said that you have to believe him. He was 5-Love down with his game and he mixed it up. It seemed like it was a bit of a lack of effort, but then he started playing great."