Defending champion Rafael Nadal's progress into the US Open quarter-finals was far from smooth as he needed four sets to beat unseeded Georgian Nikoloz Basilashvili.
The 32-year-old Spaniard led by two sets to love before Basilashvili, ranked 37th in the world, recovered to take a third-set tie-break.
But the top seed broke twice as Basilashvili faded physically in the fourth to win 6-3 6-3 6-7 (6-8) 6-4.
He faces ninth seed Dominic Thiem next.
Austria's Thiem knocked out South African fifth seed Kevin Anderson - the man who lost in the Flushing Meadows final to Nadal last year - in three sets earlier on Sunday.