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French Open finalist Paolini progressed to the last eight with a 6-3 6-7 (6-7) 5-5 victory, though the Italian was on the brink of an exit before that.

The seventh seed trailed 5-2 in the deciding set before dragging back into the contest by winning two games, with Keys then calling for the physio and a medical time-out due to a thigh issue.

American Keys was visibly distraught after leaving the court for treatment, returning to concede another game and struggling to serve before retiring with the game finely poised.

Paolini will now face either Emma Navarro or Coco Gauff in the quarter-finals at SW19.

Paolini became the first Italian in the Open Era to reach the women's singles quarter-final at Wimbledon and Roland-Garros in the same season, having fallen in the French Open final to Iga Swiatek.

Having never won a match at Wimbledon before this year, Paolini has now won four straight, though this triumph came in unwanted circumstances.

Keys is only the second player in the Open Era to retire in the third set of a women's singles round-of-16 clash at a major, after Julie Heldman progressed past Billie Jean King via retirement at the US Open in 1973.