Cincinnati, OH, USA, 19 August 2016 | AAP

Bernard Tomic has continued his stellar week at the Cincinnati Masters, upsetting fifth seed Kei Nishikori.

With the win, the Australian claimed his biggest scalp in five years.

Tomic outlasted the Rio Games bronze medallist 7-6(1) 7-6(5) to book a likely quarterfinal against new two-time Olympic champion Andy Murray.

This will be Tomic’s third appearance in an ATP Masters quarterfinal, after reaching the same stage at Indian Wells and Shanghai in 2015.

Nishikori is 23-year-old Tomic’s highest-ranked win since Wimbledon in 2011, when he upset then world No.5 Robin Soderling.

However, it’s the second time the Queenslander has beaten Nishikori this year – he also knocked him out of the season-opening Brisbane International, when the Japanese star was ranked No.8.

Top seed Murray was due to face Kevin Anderson in their third round clash later on Thursday (Friday AEST).

A day after beating 11th seed David Goffin, the world No.21 Tomic’s serve was again on song as he approaches the final major of the year at Flushing Meadows.

He sent down 10 aces and was broken just once, early in the first set.

In the women’s event, the exciting run of Daria Gavrilova came to an end.

The Aussie, who began the week in qualifying and won four straight matches to reach the third round of the main draw, went down to third seed Simona Halep.

Halep’s 6-1 6-2 win in 53 minutes set up a quarterfinal meeting with either Agnieszka Radwanska or Johanna Konta.