Rafael Nadal will overtake Andy Murray to reclaim the world number one ranking next week after Roger Federer announced his withdrawal from the Western & Southern Open in Cincinnati with a back problem.
Only Federer could have prevented the Spaniard from returning to the summit for the first time since July 2014, with Murray guaranteed to be toppled as he continues his recuperation from a hip problem.
The Scot, who lost to Marin Cilic in the 2016 Cincinnati final, will lose 600 points, meaning Nadal would usurp him even if the 31-year-old followed his big-name rivals in withdrawing from the tournament.
Nadal is the only player in the world's top six still standing in the Cincinnati event, with Federer now joining Murray, Cilic, Novak Djokovic and Stan Wawrinka on the sidelines.
Apologising to Cincinnati fans in a statement, Federer said: “Unfortunately, I tweaked my back in Montreal and I need to rest this week.”
Nadal could have reclaimed the world number one spot by reaching the semi-finals in Montreal last week, but fell to Denis Shapovalov in the third round.
