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Sinner, who was crowned the Australian Open champion last month, started the 2025 season in stunning fashion with the third grand slam success of his career in Melbourne. 

The world number one beat Alexander Zverev in straight sets in the final, becoming only the fourth player since the start of 1990 to not face a single break point in a men’s singles final at a grand slam, after Pete Sampras (Wimbledon 1995), Roger Federer (Wimbledon 2003) and Rafael Nadal (US Open 2017).

Sinner is also just the fifth man in the Open era to win three consecutive singles titles at the hard-court slams, while he also became the youngest player to win back-to-back men's singles titles at the Australian Open since Jim Courier (1992-1993).

However, Mouratoglou believes the 23 year-old is still not the best player in the sport. 

Mouratoglou, who previously coached Serena Williams, suggested that Alcaraz, who claimed two grand slam titles in 2024, was above Sinner in terms of performance. 

"Jannik is not above everyone; I don’t think he’s above Carlos," Mouratoglou said. "I think when Carlos is at his best there is a real match, and I’m not sure who is going to win.

"Nobody can say who is going to win. All their matches have been extremely close. Carlos won some big ones against him. So I wouldn’t say that [Sinner] is above [Alcaraz].

“Those two—[Jannik] and Carlos—are above everyone else."

Since the start of 2024, Sinner’s dominance has been unrivalled. He won nine titles, and lost just four of 72 Tour-level matches in which he won the first set – three of those defeats came to Alcaraz.

The Spaniard holds a 6-4 record over Sinner in their most recent meetings, with his win in the China Open final his third consecutive victory over him. 

Alcaraz was quick to relay the records Sinner has achieved over the past year, adding that the world number one's positioning in the ATP rankings was deserved. 

"Jannik has proven to be the best at the moment, it's crazy what he's doing," Alcaraz said. 

"I understand that people argue about who is the best between us two, but for me and for the tennis players who play against him, Jannik is definitely the strongest.

"I don't agree with what Mouratoglou said. Jannik will have lost 4/5 matches in a year. He has no ups and downs.

"In every tournament he participates in he either reaches the final or lifts the trophy."