Roger Federer and Rafael Nadal boosted in world No.1 chase as Andy Murray withdraws from Cincinnati Masters

Andy Murray will officially be replaced as world number one before the US Open after withdrawing from the upcoming Cincinnati Masters due to an ongoing hip problem. The three-time grand slam champion has been atop the ATP standings since last November, but either Roger Federer or Rafael Nadal will take over come the fourth major of the year at Flushing Meadows.

"Unfortunately I won't be playing in Cincinnati as I continue my recovery," Murray said, who finished 2016 as the world number one after winning 24 matches in a row. "I always enjoy playing there and I look forward to returning next year. I'm continuing to work hard on the court with the aim of being in New York."

Injury hindered Murray during his run to the Wimbledon quarter-finals and forced him to pull out of this week's Rogers Cup in Montreal, the first significant event of the American hard court season. Though he had no points to defend in Canada he did reach the final in Cincinnati, and upon the rankings being recalculated after that second Masters 1000 event Murray will find himself off the top regardless of Nadal or Federer's performance over the next fortnight.

Spaniard Nadal is the favourite to return to world number one for the first time since June 2014 in Montreal and will do so if he reaches the semi-finals. Federer meanwhile has no points to defend for the remainder of the season and, should he remain fit, could replace Nadal in Cincinnati – though he may have to reach the final in both events.

Ten-time French Open winner Nadal faces Borna Coric of Croatia in his opening match this week and could face Juan Martin del Potro, who beat him at the Olympic Games this time last year, for a place in the last eight. Milos Raonic is likely to lie in wait in a match that, should Nadal win, would see him underline his remarkable return in 2017.

Meanwhile, a second tournament withdrawal in a row for Murray throws into doubt his participation in the US Open in New York, which starts on 28 August. The British number one has so far avoided surgery and opted for rest rather than going under the knife in a procedure that would curtail his season.

Whether Murray will be willing or able to play through the pain barrier in an effort to revive his campaign remains to be seen. The hip problem severely hinders his court coverage – one of his defining traits – and was apparent during the latter stages of his loss to Sam Querrey at SW19.