Frances Tiafoe delivered another upset win over Stefanos Tsitsipas, with the American beating the ATP No. 3 3-6, 6-3, 6-4 on Thursday to book into the quarter-finals of the ATP Vienna event.
Tiafoe backed up his win over the former ATP Finals champion with a first-round Wimbledon shocker three months ago while losing to the Greek at the Olympics.
The 49th-ranked Tiafoe rallied from 0-3 down in the final set to escape with the victory.
He now faces Diego Schwartzman in the quarters after the Argentine put out Gael Monfils 7-6(5), 4-6, 6-2.
Tiafoe needed less than two hours to eliminate Tsitsipas, who hammered 11 aces but was broken three times.
The American has lost twice this season to Schwartzman, in the second round at Barcelona and Cincinnati.