PARIS (Reuters) - World number one Novak Djokovic reached his 10th French Open semi-final but suffered an injury scare before beating Spain's Pablo Carreno Busta 4-6 6-2 6-3 6-4 on Wednesday.
A month after being defaulted for inadvertently 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 apparent physical problems with the top seed wearing tape on the back of his neck and his upper arm requiring treatment.
Carreno Busta, who lost in the U.S. Open semi-final after leading Alexander Zverev by two sets, took advantage to win the opening set -- the first conceded by Djokovic in the tournament.
Djokovic looked flat and had to save break points early in the second set before raising his game at the important moment to win the next two sets.
Carreno Busta hung on gamely but Djokovic was superior when it mattered and one break in the fourth was enough to set up a last-four clash with Greek Stefanos Tsitsipas, the Serb's 38th Grand Slam semi final.
Djokovic's dramatic demise in New York deprived him of a chance to win an 18th Grand Slam title and move to within one of Rafa Nadal's haul and two shy of Roger Federer's men's record.
He looked relieved after avoiding another setback against the Spaniard he has found such an awkward customer of late.
"I started this match a bit badly with bad movement. After I found rhythm and confidence," Djokovic said afterwards on Court Philippe Chatrier on another damp and chilly night.
"It was important to stay focussed. Many players have said it before me: these four Grand Slams matter the most in tennis history."
Djokovic looked stiff and his swings restricted in the early exchanges and he fired a forehand into the net to lose serve at 2-2, but broke back in the eighth game.
However he was banging his racket against his thigh in frustration as he dropped serve again before Carreno Busta held to take the opening set.
The alarm bells were ringing for Djokovic when he faced two break points at 1-1 in the second set but he saved them before raising his level to square the match.
It began to look like plain sailing when he led 3-0 in the third set before a dip allowed Carreno Busta back to 3-3 and the Spaniard wasted a break point when he went for glory on a forehand during a long baseline exchange.
Djokovic then reeled off three games to take the third set but was roaring in frustration as he missed four break points at 1-1 in the fourth and another at 2-2.
He did get the break at 3-3 but still Carreno Busta was dangerous and had chances to respond immediately.
But Djokovic was determined to avoid a late night and completed an often laboured victory with a forehand winner.