Take this for what you will....
Federer is a bit less than 5 years older than Nadal. Sinner is exactly 5 years older than Fonseca. Federer had his first hugely dominant season in 2004 at age 22-23; Sinner dominated the tour in 2024 at age 22-23. Rafa joined Roger at the top in 2005 at age 18-19. Fonseca is 18-19 in 2025.
Meaning, if 2024 is for Jannik what 2004 was for Roger (same age), then 2025
could be for Fonzie what 2005 was for Rafa.
No, I am not saying SInner is as good as Federer or Fonzie as good as Roger, but that the ages are the same relative to each other. Something to keep in mind, as Fonzie rises. He's as young relative to the #1 player as Rafa was to Federer - and seeming breakout years are the same.
Another similarity is that both Federer and Sinner were relatively late bloomers, coming fully into their power at age 22-23 (even though both were
Now of course there's Alcaraz in the mix, so the comp diverges there. Alcaraz is 1 year and 9 months younger than Sinner, and 3 years and 3 months older than Fonseca, so much closer to Sinner and part of the same generation, really. I've also show the similarities between Sinner and Federer's ranking trajectories, and Rafa's and Alcaraz's, which you can see here:
Fonseca is obviously the outlier, but that's mostly (even entirely) due to fewer ATP tour matches played: through 2024, he had played in only 7 ATP level tournaments. At the same age, Roger had played 17, Rafa 30, Sinner 10, Alcaraz 20. So really, the more important rank comp will be this year - and we shouldn't be disappointed if he's more in the Federer/Sinner range than the Nadal/Alcaraz range. But we shall see...Before watching his performance against Rublev, I was predicting he'd finish #38 or so (I think, can't remember the exact number)...now I'm predicting #18.