Novak Djokovic says it was a "a very awkward situation" when a ball flew off his racquet into a line judge's face during a French Open fourth-round win.
The 33-year-old Serb was defaulted from the US Open last month when he hit a line judge after swatting away a spare ball in frustration.
This time - in a straight-set win over Karen Khachanov - there was no chance of a default as the ball was still in play and it was not a dangerous action.
"I hope he's fine," Djokovic said.
"He dealt with it in a strong and brave way.