Carlos Alcaraz has publicly acknowledged that he wants to break records. Jannik Sinner hasn't distinctly acknowledged so but wouldn't mind breaking a few in the future. However, breaking records isn't something that happens every day.
Grand Slam records are even less achievable because, in the tremendously long history of tennis, only a few have achieved so. Novak Djokovic is one of them, as he's the player with the most Grand Slam singles titles (24). That number used to be much smaller, and people assumed that whoever got to 20 would probably write their name in the history books.
So, can someone else get to this number and possibly exceed it? Carlos Alcaraz would like to believe he could because he has admitted to it. He didn’t say specifically that he will win 25 Grand Slams but admitted wanting to be the best player ever. Considering that this achievement is the most prestigious one, he can’t become that without getting to this number.
Can he do so? Perhaps, perhaps not. The Spaniard is 22, and barring something catastrophic, he should be able to play at least a decade, if not more. It means he will have a chance to possibly compete in 40 Grand Slams. To get to 25, he will need to win 21 more, which would be around half of those in which he would compete.
Is that impossible? It’s not, but it might not be humanly possible. There are many factors that will determine that, but it looks improbable. Alcaraz himself has toned down some of the narratives he used to embrace earlier in his career because he probably realized that some of them are frankly unlikely.
Jannik Sinner, meanwhile, has had a much more measured approach, compared to Carlos Alcaraz, but that’s no wonder because he has fewer Grand Slams. Not many fewer, because he’s up to three himself, but neither of them is close to 10 yet, so that will be the first big hurdle they will need to overcome.
Carlos Alcaraz is unlikely to hit Novak Djokovic’s numbers

The reality of the situation is that Alcaraz is very unlikely to hit Djokovic’s numbers purely from a statistical standpoint. It can be done, and if he does, he will be hailed as the legendary player he already is, but it’s still unlikely.
Former player Laura Robson seems to think that the conversation about hitting those numbers is quite absurd. Robson, who isn’t known as a Djokovic supporter by any means, simply knows how improbable it is.
“They are talking about getting three or four Grand Slams a year to hit Novak’s numbers. To be even thinking about that is kind of absurd.” - Laura Robson on Alcaraz.
It might not be as absurd if you are as good and as motivated as Carlos Alcaraz or even Jannik Sinner, for that matter. What's kind of absurd is thinking that it’s realistic because it’s not. Alcaraz has already shown himself to be struggling massively against other players. He’s also had injury issues, and many have singled out his playing style as one that's not likely to last into his thirties.
Even if everything goes swimmingly — which it’s not likely to do — winning 50% of all Grand Slams you attend would be a historic winning rate not seen from too many players in the past. It’s just not likely to happen, but that doesn’t mean it’s impossible.
People called the record of Sampras (14 Grand Slam titles) something impossible, but we have had three players eclipse it — and by a lot. There will be more in the future, but whether those players get to 20 or beyond remains to be seen.
Perhaps if Alcaraz is there in five years at age 27 with 14 or 15, this discussion will pop back up, as it would be infinitely more realistic than it is now. The closer he gets to the actual number, the more the conversation will heat up.
Now, sitting at only four, it’s too early to talk about that. Robson is right — while perhaps not absurd, it’s not something that should be the focus when it comes to Alcaraz or Sinner because they are unlikely to get there.
It’s just reality, and it’s also proof of how good the big three truly were at their peaks. There's a reason why they are talked about as the giants that will never be eclipsed. It’s because they are precisely that.
How did Novak Djokovic meet Jelena Ristic? All about the most admired couples in tennis