Memphis, USA, 22 February 2013 | AFP/

Australian Marinko Matosevic is through to the quarterfinals of the US National Indoor Tennis Championships with an upset victory over fourth-seeded American Sam Querrey on Thursday.

Matosevic emerged a 3-6 6-4 7-5 winner, and in the last eight will face Alexandr Dolgopolov, who overcame local qualifier Rhyne Williams in three sets.

In the first meeting between the pair, little separated them on the stats sheet except for in the aces department, with Matosevic forced to survive a barrage of 15 from his big-serving opponent, ranked No.21 in the world.

Yet the Aussie held firm – he scored one more service break than Querrey, enough to help him seal victory in just under two hours.

Earlier in the day in Memphis, Lleyton Hewitt went down in his second round match, routed by Denis Istomin.

The Uzbek dismissed Hewitt 6-1 6-2 in just 58 minutes, thoroughly dominating the match in every aspect.

While Istomin was dominant on serve, banging down seven aces and winning almost three quarters of points behind his first serve, Hewitt struggled with his delivery – the Australian produced six double faults, won just 27 per cent of second serve points, and was broken four times.

With the win, Istomin levelled his head-to-head with Hewitt at two matches each, with the world No.63 also winning their match at the Brisbane International in January.

Istomin moved through to the quarterfinals where he will face American Michael Russell.