Key to 'remarkable' Roger Federer success revealed by Andy Murray's former coach

Roger Federer's ability to defeat opponents in double-quick time has been key to the 20-time Grand Slam champion's stunning revival, according to Andy Murray's former coach Miles Maclagan.

The 36-year-old added another achievement to his glittering CV by becoming the oldest world number one in tennis history – eclipsing Andre Agassi – after winning the Rotterdam Open.

Returning to the top of the ATP standings, five-and-a-half years after his last appearance, caps a stunning 14 months for Federer since his return from a knee injury which curtailed his 2016 campaign.

The Swiss legend has won three of the last five Grand Slam titles, helped by adapting his schedule to manage his fitness and extend his career.

In Rotterdam, Federer took less than an hour to beat Ruben Bemelmans in round one and then Grigor Dimitrov in the final – with his new found-attacking guise paying dividends once again.

And Maclagan, who worked with Murray between 2007-10 and also coached the Great Britain Davis Cup team, believes the ability to end matches quickly is central to Federer's Indian summer.

"It's absolutely remarkable," he told Sky Sports. "This is sort of a small example of his career, the fact that he's still fresh at the end of a tournament. The way he's managed himself, the manner in which he is able to come through and have this sort of performance in the final and outclass the number five player in the world.

"He really didn't [put a foot wrong]. He made probably zero incorrect shot selection decisions. He was potent behind his first and second serves. There was pressure coming on to Dimitrov from every single area of his game."

He added: "We're not used to that on the men's tour. The minimal stress on the body, the emotional stress that he doesn't have to go through because the matches are relatively simple.

"Maybe Grigor Dimitrov wasn't 100% or Robin Haase either as we saw an unfortunate incident at one stage where he had his head in the bin.

"Roger has got better and better which is absolutely remarkable to everybody. He's got back to number one but he was a contender for most improved player of the year last year. He just continues to astound us."