Rafael Nadal says he was "wrong" to take Lorenzo Sonego to task at the net as his "best match" of Wimbledon this year ended on a testy note.
The Spaniard won 6-1 6-2 6-4 with a stunning display to reach the fourth round that showed a marked improvement on his first two matches.
But it ended with boos as Nadal continued a discussion with Sonego, having had words in the third set.
"I should not call him [to] the net," Nadal, 36, told a news conference.
"I have to say that I was wrong. So apologise for that. My mistake in that. No problem. I recognise that."
The roof came on with Nadal leading 4-2 in the third, with the Spaniard appearing unhappy at the interruption.
Two games later he was upset over a noise Sonego had made during a point as the 27-year-old Italian set up his first break points of the match.
Nadal spoke to the umpire but then called Sonego to the net to speak to him, with the Spaniard then going on to lose his serve.
"My intention was never to bother him at all. Just to tell [him] one thing that was bothering me that I think he was doing in that moment, but that's it," Nadal said.
"I think there is some codes between players. We had some issues there. But that's it."
While Nadal then regained control over a match he had dominated and wrapped up victory quickly, he carried on speaking to the Italian at the net after they had shaken hands at the end.
In his on-court interview, Nadal said he felt sorry if he "bothered him", saying he "did it in a right way" but later said he had spoken to Sonego in the locker room and apologised, adding he did not want to comment on the specific issues in the match.
Nadal dominance underlines title credentials
Before that episode Nadal had made serene progress in a thoroughly dominant display that underlined in emphatic style his claim to a third successive Grand Slam title.
Just a day after main title rival Novak Djokovic had come through a similarly one-sided match, Nadal sent his own message back.
The Spaniard dropped just two points on his serve in the first set and did not face a break point until the eighth game of the third set.
He won nine games in a row to take the first set and put himself in command of the second before world number 54 Sonego got back on the board with a hold that the Centre Court crowd cheered as if he had won the set.
Early in the third set the Italian had suggested to the umpire that the light was fading and that it might be time to switch on the lights, but it was not until 4-2 when his wish was granted.
He went on to break to love, a game in which he greeted one of his own spectacular shots noisily, thus irritating his opponent, but Nadal recovered to win the next two games to set up a last-16 match against Dutch world number 25 Botic van de Zandschulp.
Nadal is making his first Wimbledon appearance since 2019 and playing in his first grass matches since then.
He had dropped a set in his first two matches but against Sonego it was as if he had never been away from the place where he has won two of his major titles.
"It was my best match without a doubt," Nadal said.
"I made a lot of things much better than the previous days - the determination, the way that I manage to play more aggressive, going to the net plenty of times."