Serbia's Novak Djokovic moved straight into the French Open semi-finals after his quarter-final opponent Fabio Fognini withdrew with a leg injury.
Fognini beat Spain's Albert Montanes 4-6 6-4 3-6 6-3 11-9 on Sunday to reach his first Grand Slam quarter-final.
But while trailing on Sunday, Fognini winced in pain at the baseline after hitting a serve and clutched his leg.
"I'm not really happy right now," said the 24-year-old. "It's the best tournament of my career."
Fognini was the first Italian to reach the men's quarter-finals at the French Open since Renzo Furlan, who lost to Sergi Bruguera in straight sets in 1995. He was also the first Italian to make it to the last eight at any major men's tournament since 1998.
"The doctors say if I play on Tuesday maybe it can be dangerous," he added.
Djokovic has won all of his 41 matches in 2011 and has an overall winning streak of 43 straight matches, but he will not be credited with a victory over Fognini because the Italian withdrew.
The Australian Open champion could meet third seed and 2009 winner Roger Federer in the semi-finals if the Swiss gets through his quarter-final against the winner of the clash between Gael Monfils and David Ferrer.