Miami (AFP) - Juan Martin Del Potro turned back a challenge by Damir Dzumhur on Thursday to book a quarter-final clash with defending champion Sam Querrey at the ATP Delray Beach Open.

Argentina's Del Potro, the 2011 Delray Beach champion playing just his second match of 2017, held on to beat the Bosnian 7-6 (7-5), 4-6, 6-3.

Del Potro, the 2009 US Open champion now ranked 42nd in the world, is making his 2017 debut this week, and the rust was evident in six double faults - five of them coming in the first set.

On Friday, he'll face world No. 35 Querrey, who blasted 13 aces without a double fault in dispatching fellow American Jared Donaldson 6-2, 6-3 in a second round match at the outdoor hardcourt event.

Also reaching the last-eight was 57th-ranked Belgian qualifier Steve Darcis, who ousted Georgia's Nikoloz Basilashvili 6-3, 7-5.

Darcis next faces 69th-ranked American Donald Young, who rallied to defeat compatriot Taylor Fritz 4-6, 6-3, 6-4.