(VIDEO) Jannik Sinner aggravated by smug fan after directed heckling throughout victory over Joao Fonseca

Jannik Sinner left the court triumphant against Joao Fonseca in a close and very tense match at Indian Wells, winning a brace of tiebreaks 7-6(6), 7-6(4). Just before the first one, he was irritated by someone in the crowd ahead of him serving, and was having none of it.

The Italian was facing Fonseca on court for the very first time in a hugely intriguing matchup. Touted as one for the future, the Brazilian has risen through the ranks at a rapid pace, already boasting two ATP titles while seeing himself as high as world number 24. Injuries at the start of the year have proved costly, but he is now finding his flow and playing some very good tennis.

He would especially need to find his best game against the world number two if he even had any chance of competing with Sinner levels above the rest of the tour, just Carlos Alcaraz sits above him. That gap is not going to close itself, with the 24-year-old in a period where he is defending no points due to the suspension last year. He will be hoping to make the most of this situation, with a title at Indian Wells the first aim on his list after what has been a slightly disappointing campaign so far.

It was a very tight first set of tennis. Both players had their opportunities to break and steal a march on their opponent, but those were retrieved by the server as a tiebreak seemed almost inevitable. Sinner had gotten the score 40-15 and was just about to serve it out to confirm that tiebreak before he lost his cool with someone in the crowd.

"Jannik, what's going on?" umpire Greg Allensworth said to Sinner as he came down from his chair to investigate the brewing situation. Sinner had been targeted and heckled throughout the match by a single fan, and now he had lost his cool with that particular individual, wandering over to give him a piece of his mind.

"If we can not talk during the point we would appreciate it," Allensworth echoed towards that selection of fans as he tried to restore order. "But now Jannick, come on," he followed by saying, trying to get the match back underway. "If there is something else going on, please let me know."

Sinner confirmed the tiebreak, but the pressure was getting to him as Fonseca created three set points. The 20-year-old is hugely popular when stepping onto the tennis court, amassing a huge number of fans who cheer him through thick and thin. However, this time he was unable to put a smile on their faces after Sinner reigned him in before a swift five-point swing stole the first set all for himself.

It looked like the second set would also be going the way of the four-time Grand Slam champion, who broke to move into a 4-2 lead. Nevertheless, Fonseca was not quite done yet, powering his way back into it by breaking to love just as Sinner was looking to serve out the match. A second tiebreak was on the cards, and this time Sinner was the one to take command. After going 4-3 down, he won the remaining four points of the match to book his spot in a third quarterfinal at Indian Wells, with a major title the ultimate aim. He will take on Learner Tien in the last-eight after the American survived a brace of match points on the way to defeating Alejandro Davidovich Fokina.