Jannik Sinner will still have the US Open on his mind, having fallen just short of successfully defending his title earlier this month.

Sinner has lost his world number one ranking following his US Open final defeat, in which he was beaten by Carlos Alcaraz.

Alcaraz has surpassed the Italian in top spot after their latest battle on the ATP Tour, which the Spaniard won 6-2, 3-6, 6-1, 6-4.

Sinner has a clear Alcaraz problem given their current standings, with their head-to-head record now reading 10-5 in favour of the latter.

He now has six Grand Slam titles to his name, two ahead of his closest rival in men’s tennis at this moment in time.

Carlos Alcaraz and Jannik Sinner with their US Open trophies.Photo by Clive Brunskill/Getty ImagesJannik Sinner urged to make change to his game after US Open final loss

The duo did, however, manage to share the four Grand Slam titles in 2025, a feat they also managed in 2024.

But after Alcaraz won their latest battle, Serena Williams’ former coach Rick Macci believes there is room for improvement for Sinner.

READ MORE: The six players who could challenge Jannik Sinner and Carlos Alcaraz at the Australian Open have already been named

He wrote on X: “The serve is the easiest part of the game to change because of no running. It is a balanced /timed action from the ground up.

“Sinner should modify/ experiment with pin point/ platform/ different takebacks. His arm is a loose wire and with a science based modification it will raise the % and location.”

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Jannik Sinner’s 2025 ATP serving stats

It is near impossible to identify a Sinner weakness right now, with that area of his game only really prevalent when he takes on Alcaraz.

The Italian has lost just five matches throughout the 2025 season so far, four of which have come against Alcaraz.

Moreover, all four have been finals, with Sinner losing out at the US Open, French Open, Italian Open and Cincinnati Open.

His other defeat came against Alexander Bublik, who really impressively won their round of 16 meeting in Halle.

Stat Total Rank % 1st serve 60.6% 54th % 1st serve points won 78.9% 3rd % 2nd serve points won 59.6% 1st % service games won 92.0% 1st Avg. aces/match 6.7 39th Avg. double faults/match 1.5 79th

Jannik Sinner’s 2025 serving stats (ATP stats)

The 2025 serving stats do, however, suggest that if one area could be worked on by the former world number one, it is his % 1st serve efforts.

It is arguably the most significant of his apparent weaknesses, with Sinner dominating various other areas of serving in men’s tennis this season.