Federer was far from his free-flowing best but he recovered from a slow start to eventually move past Indian qualifier Nagal 4-6 6-1 6-2 6-4 at Flushing Meadows.

The 20-time grand slam champion – who suffered a shock defeat last time out at the Western & Southern Open in Cincinnati – will next meet Damir Dzumhur in his pursuit of a first US Open title since 2008.

Nagal was not overawed under the bright lights on Arthur Ashe, where Federer looked comfortable in the opening two games but that was until errors started to creep in – the Swiss star recording 19 unforced errors in the first set.

World number 190 Nagal – aggressive from the baseline – benefitted from a couple of errors and a backhand shank to earn a pair of break points. Federer saved the first, but a double fault handed the break straight back to his unheralded opponent.

It did not get any better for Federer, who shanked another backhand as Nagal broke at 15-40 for a 5-4 lead before sensationally serving out the set.

Nagal continued to delight the Arthur Ashe crowd with his forehand winners down the line. But while Federer continued to spray some of his shots either wide or long, he managed to break after a marathon second game.

It was a confidence-boosting game for Federer, who slowly began to find his feet as he moved clear 4-0, much to the relief of his box and supporters.

Federer had six chances to win the set and level the match but he struggled to close it out, though he was not to be denied at the seventh time of asking thanks to a Nagal error.

Nagal was unable to keep up with Federer, who broke twice in a relatively comfortable third set to move ahead in the match for the first time and he never looked back, despite fending off four break points before serving it out.