Paris: Top seed Novak Djokovic passed his first real test at this year's French Open with flying colours as he battled past Russia's Karen Khachanov 6-4, 6-3, 6-3 on Monday to reach the quarterfinals for the 14th time.
The 33-year-old claimed a fourth successive straight-sets victory in his latest quest for a second French Open title, but it was nowhere near as straightforward as the score suggests.
Djokovic faced stiff resistance before taking the first set and had an anxious moment when his attempted return off one Khachanov serve ricocheted off his frame and struck a line judge in the head, reviving memories of his US Open debacle.
Khachanov saved four set points at 2-5 in the second set before Djokovic moved two sets clear.
Djokovic appeared to be in cruise control when he led 2-0 in the third but Khachanov took the next three games and had two break points for a 4-2 lead.
The Serb held, though, and regained control to ease into his 47th Grand Slam quarterfinal where he will face 17th seed Pablo Carreno Busta, the man Djokovic was facing in the US Open fourth round when he was defaulted for hitting a line judge with a ball.
Altmaier's impressive run ends
German wildcard Daniel Altmaier's impressive run was ended emphatically by Carreno Busta as the Spaniard claimed a 6-2, 7-5, 6-2 victory late on Monday.
Carreno Busta had to weather a second-set fightback by the 22-year-old but proved too experienced as he reached the quarterfinal for the second time.
Altmaier had already dispatched seeds Jan-Lennard Struff and Matteo Berrettini and was hoping to become the first player to reach the quarterfinal of his maiden Grand Slam appearance since Alex Radulescu at Wimbledon in 1996.