Spanish top seed Carlos Alcaraz continued the defence of his US Open men’s title with a straight-set win over South Africa’s Lloyd Harris.
Alcaraz, 20, was made to work hard in the third set before sealing a 6-3 6-1 7-6 (7-4) victory in New York.
Third seed Daniil Medvedev won 6-2 6-2 6-7 (6-8) 6-2 against Chris O’Connell.
Russia’s Medvedev, who won his sole major at Flushing Meadows in 2021, was cruising by two sets and a break up before he allowed the Australian back into the contest.
Medvedev, 27, lost his serve as 69th-ranked O’Connell levelled for 4-4 in the third set and could not convert two more break points at 5-5.
The former world number one had two match points in the tie-break, producing a double fault on the second, then another on set point, as O’Connell prolonged the match.
Medvedev regrouped to move 4-1 ahead in the fourth set, fighting off three break points for 5-2 and finally closing out victory at almost 01:10 local time.
Meanwhile, John Isner brought the curtain down on his professional career as the American veteran lost a five-set thriller to compatriot Michael Mmoh.
Isner, 38, lost 3-6 4-6 7-6 (7-3) 6-4 7-6 (10-7) as Mmoh fought back from match point down to win a tense fifth-set tie-break.
Elsewhere, Italian Matteo Berrettini is out after retiring when trailing 6-4 5-3 to France’s Arthur Rinderknech.
The former semi-finalist badly twisted his ankle chasing down the ball as Rinderknech served for the set and, after a long period on the floor in clear pain, decided he could not continue.
Sixth seed Jannik Sinner eased through with a 6-4 6-2 6-4 win over another Italian, Lorenzo Sonego.
German 12th seed Alexander Zverev, the 2020 finalist, set up an eye-catching meeting with Andy Murray’s victor Grigor Dimitrov by battling past Daniel Altmaier in four sets.
