Nadal fights off Querrey

three break chances by Wawrinka, who could not match the uptempo play of Murray after a gruelling five-set win over Italian Flavio Cipolla in round three.

Murray moved into the round of 16 for the first time in his three appearances at the US Open, where he will face 19-year-old Juan Martin del Potro of Argentina.

In a battle of talented teenagers, del Potro emerged with a 6-3 6-4 6-3 victory over 18-year-old Kei Nishikori of Japan.

Del Potro, who has won four titles since July, extended his winning streak to 23-matches. He is the first player in ATP Tour history to win his first four titles in four straight tournaments.

Men's Singles Fourth Round
1-Rafael Nadal (Spain) def. Sam Querrey (USA) 6-2 5-7 7-6 (7-2) 6-3
Mardy Fish (USA) def. 32- Gael Monfils (France)) 7-5 6-2 6-2
17-Juan Martin Del Potro (Argentina) def. Kei Nishikora (Japan) 6-3 6-4 6-3
6-Andy Murray (Great Britain) def. 10-Stanislas Wawrinka (Switzerland) 6-1 6-3 6-3