Andy Murray wins in Cincinnati heat

Murray, who clutched at his right shoulder after going an early break down to trail 3-2 in the first set, soon snapped into focus to run off four games in a row on his way to a 6-3, 6-2 victory.

Nadal, the third seed, showing fatigue following a busy Olympic schedule that included a gold medal in doubles, was a step off the pace and paid the price against the 19-year-old Borna Coric of Croatia, who reached the last eight with a 6-1, 6-3 win.

Elsewhere, Grigor Dimitrov eliminated the sluggish second seed Wawrinka, the Bulgarian making the most of a single break of serve in each set to win 6-4, 6-4 and book his berth in the quarters.

Coric advanced to his first ATP Masters quarter-final, dominating Nadal by reeling off 10 straight games to claim the opening set and lead 4-0 in the second.

The Bulgarian will next face the American Steve Johnson, who saved four set points as he advanced to the quarters over the seventh seed Jo-Wilfried Tsonga of France 6-3, 7-6(6).