Juan Martin Del Potro staged a remarkable comeback from two sets down to beat sixth seed Dominic Thiem to reach the US Open quarter-finals.
The 2009 champion was struggling with illness from the outset and received treatment in the first set.
With the crowd behind him, the Argentine saved two match points and rallied to take it to a decider, coming through 1-6 2-6 6-1 7-6 (7-1) 6-4.
Del Potro will now face either Roger Federer or Philipp Kohlschreiber.