A month after being defaulted for striking a line judge with a ball while playing Carreno Busta in the U.S. Open fourth round, the 33-year-old Serbian found himself in trouble once again.
This time it was nothing more sinister than pains in his neck and arm as Djokovic lost the opening set to the 17th seed — the first one he has dropped in the tournament.
Djokovic looked flat and had to save break points early in the second set before raising his game to level the match.
It looked plain sailing when he led 3-0 in the third set before a dip allowed Carreno Busta back but Djokovic saved a break point at 3-3 before pulling away.
Djokovic, bidding for a second French Open crown, produced several loud roars as he tried to fire himself up.
Carreno Busta hung on gamely but Djokovic was superior in the big moments and one break in the fourth was enough to set up a semi-final clash with Greek Stefanos Tsitsipas. (Reporting by Martyn Herman, editing by Ed Osmond)