Didn't this kind of diplomacy give a player Poland an early partition?
Well, only if russian player, is very good. And Alfonso, who played novgorod, was not realy playing well. Also it would need quite good austrian player too(austria do not have bigger army than poland - at least not bigger enough to feel safe with poland warning it. Actualy allowing austria to take croatia, is kind of dumb, as it means strenghtening it.
Also, ottomans have much things to do, and if you won't manage to screw them up, they will propably agree on status quo. And if you succed in taking down ottomans, you are pretty much won (aspecialy with PU on bohemia, and propably hungary). Austria would not dare to fight a poland who owns bohemia and hungary and army that keeps lithuania not insulting them(around 35K troops).
Also, remember that russia is just weak compared to poland lithuania early. Not like i mean guaranteeing russian minors atb - you would have not enough diplomats. But if russian player is novgorod, he propably do NOT conquer any of russian minors too fast. Muscowy player could do so, but if player is muscowy you just ally/guarantee novgorod.
No early polish partition is possible with good polish player. Who would be so powerfull to make a patrition? It would need all its neighbours to attack it (Austria, Bohemia, Teutons, Brandenburg, russia etc). Very unlikely.