"You always tend to play better against better players and I'm happy to be back in the second week of Wimbledon".
Andre Agassi has described "timeless" Wimbledon favourite Roger Federer's exploits in the twilight of his career as "unexplainable".
But Federer offered a contrasting view in his media conference following a 6-0 7-5 6-4 fourth-round win over Adrian Mannarino on Monday.
Federer's performance was reassuringly familiar, though, as he displayed his typical panache and class with some cute drop shots and trademark backhand slice.
Five-time champion Venus Williams battled into the third round with a 4-6, 6-0, 6-1 win over Romanian qualifier Alexandra Dulgheru. She was joined in the third round minutes later by 10th-seeded Madison Keys of the United States, who dispatched Luksika Kumkhum of Thailand 6-4, 6-3.
Williams is seeded 25th after returning from having a baby, but is looking like her usual dominant self on the grass courts.
Top seed Federer, 36, has now won 32 consecutive sets at Wimbledon, just two behind his record set from the third round in 2005 to his title triumph in 2006. "I knew we were both moms, and I'm not sure how often that's happened, if ever".
Novak Djokovic is Nishikori's next challenge after the three-time champion thumped Russian Karen Khachanov 6-4 6-2 6-2 in an ominous display. "So it's an important moment", said Nadal, the 17-time Grand Slam champion who has made four successive quarter-finals at the majors for the first time in six years.
Bertens hit seven aces and saved eight of the 10 break points she faced to win 6-3, 7-6 (2) against Pliskova and complete the latest upset in the women's draw. His fourth-round match against Gilles Simon was suspended because of bad light after the fourth-seeded Argentine lost the third set.
Cibulkova was aggrieved before the tournament when her place as the 32nd and final seeded player was taken away as seven-time champion Serena Williams was given special dispensation by the All England Club on her return from pregnancy.
The 12th-seeded Ostapenko was given a code violation for receiving coaching while beating Aliaksandra Sasnovich of Belarus 7-6 (4), 6-0.
In the first round, Williams started by ceding a tiebreaker against 58th-ranked Johanna Larsson before taking 12 of the last 15 games.
Venus reached her ninth Wimbledon final a year ago, but the American star was denied a sixth title by Garbine Muguruza.
The eight-time Wimbledon victor will play either Ivo Karlovic or Jan-Lennard Struff in the third round.
After serving out for the first set, Federer didn't drop a single point on his serve in the second and kept that streak going until he was 30-0 up at 4-1 in the third - when Lacko finally sent a backhand victor down the line. After the review confirmed the ball landed on the line, umpire Juan Zhang of China awarded the point to Cibulkova.
Top seed Federer admitted before the match that he can still get nervous walking out on to Centre Court but he was at his free-flowing best against Lajovic who was little more than a prop in Federer's magic show.
After seven minutes, the decision was finally changed and the point replayed.