Novak Djokovic argued with the umpire and roared with delight as the Serbian brushed aside Ernests Gulbis to reach the last 16 at Wimbledon.
Djokovic came back from a break down to win the opening set and from there his victory was never in doubt as the 12-time major champion won 6-4 6-1 7-6 (7/2).
The world number four, however, apologised after the match to umpire Jake Garner, whom he had told to "focus" after seeing two early challenge requests rejected.
More ominous for his rivals, however, was that Djokovic seemed to have some of his old fire back on Centre Court, yelling in celebration as he stormed clear in the decisive tie-break.
Djokovic will now face France's Adrian Mannarino, who was a surprise winner earlier on Saturday against compatriot Gael Monfils.
The collision with Garner came before even three games had passed as Djokovic twice tried to challenge a call and each time was informed he was too late.
An angry Djokovic said: "That's two points in a row, beginning of the match. Focus, please."
Asked afterwards about the disagreement, Djokovic told the BBC: "Maybe it was not the right words to say, I apologise. It was just very odd in the third game two situations where I thought the call should have been different.
"But he is trying to do his job the best he can, I am too. In the heat of the moment you exchange things and I think we will be fine."
The display of irritation might make wary those predicting Djokovic will win a fourth Wimbledon title next weekend, but after reaching his 10th fourth round here he is yet to drop a set.
"I am delighted with the performance," Djokovic said.
"I thought I raised the level of tennis compared to the last couple of matches and last couple of weeks. It was the most focused I was on court and at the right time.
"Gulbis presents a great challenge. He is very unpredictable, he has a huge serve at 125, 130 miles per hour and on grass it's not easy against a big server like that.
"He started very well. He was a break up and I managed to win seven or eight games in a row, which gave me lot of confidence. In general I'm very pleased with how I felt I played."
Gulbis, rated in the top 10 only three years ago, has plummeted to 589th due to a combination of fitness and commitment issues but the Latvian was able to enter the main draw at SW19 with the help of a protected ranking.
He started well, capitalising on his opponent's early angst to break and lead 3-1, but a trademark backhand pass prompted Djokovic to fight back.
Serving to stay in the set, Gulbis missed three simple forehands and Djokovic pounced to win his fourth successive game and move one frame clear.
Four became nine in the second as Djokovic led 5-0, and at the end of the set Gulbis took a medical time-out for treatment on his back.
He offered more resistance when he returned but Djokovic proved too strong in the tie-break as another errant forehand confirmed his progress after two hours and 13 minutes.