World number one Novak Djokovic survived a huge scare as he fought back from two sets down against teenager Lorenzo Musetti to reach the French Open quarter-finals.
His Italian opponent retired in the fifth set.
Top seed Djokovic was outplayed by an inspired Musetti as he lost two tiebreaks, but the match then changed dramatically as the Serb fought back to win 6-7(7) 6-7(2) 6-1 6-0 4-0.
It was unclear exactly what happened to world number 76 Musetti whose stylish game was threatening to send Djokovic to his earliest Roland Garros exit since 2009.
Having produced tennis of the highest calibre in two sensational sets, Musetti then lost the third set in 24 minutes and did not even get a point in set four until the fifth game as the match slipped away from him.
A relieved Djokovic went 4-0 ahead in the decider before Musetti decided he could not continue.
It was an anti-climactic end to what was brewing up to be a seismic shock in a tournament full of surprises.