Novak Djokovic reached his 11th consecutive French Open quarter-final with a straight-sets victory against Russian 15th seed Karen Khachanov.
The world No 1, whose only title at Roland Garros came in 2016 when he completed the career Grand Slam, was pushed hard at times on his way to a 6-4 6-3 6-3 win.
Djokovic, unbeaten in 35 completed matches this year, is yet to lose a set in Paris as he continues his pursuit of an 18th Grand Slam title.
The Serbian will play 17th seed Pablo Carreno Busta in a repeat of their US Open fourth-round encounter, which ended in him being defaulted for inadvertently hitting a line judge with a ball.
Carreno Busta beat German qualifier and Sky Scholar Daniel Altmaier 6-2 7-5 6-2.
Djokovic, 33, lost only 15 games in his first three matches but the early signs under the Court Philippe Chatrier roof suggested this would be his toughest examination so far.
He converted his fifth break point of the opening set in the eighth game to secure the first break, but Khachanov immediately broke back only to lose his serve for the second successive time to hand Djokovic the set.
Djokovic began to toy with Khachanov, who beat the top seed in the Paris Masters final in 2018, and increased his ascendency by breaking the Russian in the fourth game of the second set.
The Serb showed his resolve to fight off four break point chances to open up a 5-2 lead, and despite squandering four set points on the Khachanov serve he eventually served out for the second set to extend his lead.
Khachanov, who reached the quarter-finals at Roland Garros last year, lost his serve in the opening game of the third set but responded quickly with a break of his own.
Djokovic saved two further break points in an eight-minute long sixth game of the third set and then backed it up with two successive breaks of the Khachanov serve to seal a hard-fought victory.
Djokovic: Hitting another line judge was 'awkward'
The Serb later admitted he had flashbacks to his dramatic US Open exit when he was defaulted after he hit a ball in frustration that struck a line judge in the throat during his fourth-round match with Spaniard Pablo Carreno-Busta.
On this occasion, Djokovic was only able to get a frame on a wide serve from Khachanov in the third set and the ball deflected into the head of the service line judge, but as it was during a point he faced no action.
"My gosh, it was very awkward deja vu," said Djokovic. "I'm actually trying to find the linesperson and see if he's OK because I saw he had a little bit of a bruise, like redness, in that place in the head where the ball hit him.
"I hope he's fine. I mean, he definitely dealt with it in a very strong and brave way. But it was a hit because I was very close.
"Obviously because of what happened in New York, people I guess are going to make the story out of this. It has happened to me and to many other players in the last 15 years that I've been on the tour.
"I've seen it a lot when the ball ricochets from the racquet and the frame, hits someone in the stands, or someone that is close to you or line umpire.
"Yeah, it was a very awkward situation, obviously."
Tsitsipas sets Rublev rematch
Elsewhere, Stefanos Tsitsipas progressed into the quarter-finals for the first time with a straight-sets victory against Grigor Dimitrov.
The fifth seed saved two set points in a well-contested second set against Bulgarian 18th seed Dimitrov as he sealed a 6-3 7-6 (11-9) 6-2 win.
Tsitsipas, who rallied from two sets down in his opening match against Jaume Munar, has now won three consecutive matches without dropping a set to underline the form in recent weeks which has seen him win 10 of his 12 matches this year on clay.
The 22-year-old, who is the first Greek player to reach the quarter-finals at Roland Garros, raced to a 3-0 lead in the first set but was later forced to save three set points at 5-3 when he served for the set.
The second set was of a high quality, with Tsitsipas unable to convert on three break point chances, eventually decided by a tiebreak, where Dimitrov squandered two set points as the Greek seized command.
"The tiebreak was where all the money went. I tried to take it point by point, I showed a lot of discipline. It was a very responsible win in the second set," said Tsitsipas.
Tsitsipas broke twice more in the third set against a dispirited Dimitrov to complete victory in two hours and 26 minutes.
He will face 13th seed Andrey Rublev for a place in the last four after the Russian beat Hungarian Marton Fucsovics 6-7 (4-7) 7-5 6-4 7-6 (7-3).
That encounter will be a rematch of last month's Hamburg final, where Rublev beat Tsitispas in three sets.
The Russian looked in trouble when he trailed by a set and 5-2 but fought back to end the run of world No 63 Fucsovics, who had shocked fourth seed Daniil Medvedev in the first round.
Rublev, who had never previously progressed past the first round in Paris, also saved three set points at 4-5 0-40 in the fourth set as he won 11 of the last 14 points to seal victory on a tie-break.
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