Olympic champion Andy Murray beat South Africa's Kevin Anderson 6-3 6-2 to reach the quarter-finals of the Cincinnati Masters.
It was Murray's 600th victory and he is on a career best 20-match winning streak, with Australia's Bernard Tomic his next opponent on Friday.
Briton Johanna Konta lost 6-7 (1-7) 6-4 6-0 to fifth seed Agnieszka Radwanska.
Rafael Nadal suffered a surprise 6-1 6-3 loss to Borna Coric, and the Spaniard admitted he is struggling physically.
He arrived in Cincinnati on Monday, on the same private jet from Rio as Andy Murray, having won the doubles and reached the singles semi-finals at the Olympic Games.