Borna Coric stunned John Isner to reach the Winston-Salem Open quarter finals, while Roberto Bautista Agut eased through.
Coric inflicted what was the in-form Isner’s first ever defeat at the ATP 250 event, claiming a 7-5 6-2 victory in their third round clash on Wednesday.
The Croatian managed to break the Isner serve three times, the American winner of titles in Newport and Atlanta recently bowing out in his home state of North Carolina.
Awaiting Coric in the last eight is Jan-Lennard Struff, who battled past Andreas Seppi 6-3 6-7 (3-7) 7-6 (7-3).
Bautista Agut, the top seed and last year’s runner up, cruised through, beating Marcos Baghdatis 6-3 6-4.
Next up for the Spaniard is Taylor Fritz after the American teenager edged Paolo Lorenzi 7-6 (7-3) 7-6 (7-5).
On the other side of the draw, seeds Steve Johnson and Chung Hyeon progressed.
Johnson, the sixth seed, was too good for Carlos Berlocq 7-6 (7-1) 6-4 and next faces Kyle Edmund after the Brit beat fellow qualifier Marton Fucsovics 6-2 6-1.
British number two Edmund, 22, beat world No. 122 Fucsovics 6-2 6-1 in North Carolina.
Chung led Julien Benneteau 6-4 1-1 when the French 2011 runner up retired, with Damir Dzumhur awaiting the South Korean after the Bosnian’s 7-5 6-3 success against Horacio Zeballos.
The last 8:
Steve Johnson v Kyle Edmund (3pm)
Damir Dzumhur v Hyeon Chung (follows)
Roberto Bautista Agut v Taylor Fritz (7pm)
Borna Coric v Jan-Lennard Struff (follows)