I could see Brez going beyond just trading the "big" 4: Jansen, Martin, Pivetta and O'Neill.
When he got here, he very quickly determined who to trade and some were big names or had more than a year of control:
Sale & Verdugo
Urias and Schreiber
Some younger players like Ammons, Robertson & Santos
I realize this might not have meant he disliked any of those guys, but rather liked the return better, but I think he has now had time to determine who he might not think is in his longer term plans.
I could see him not only looking very closely at McGuire, with team control that ends after 2025, but also others. I'm not an expert on what Brez likes and dislikes about players, but we might be surprised at a player or two he traded, this summer or winter.
I don't think anyone was shocked he traded Sale, Verdugo and Urias. The returns upset, some, but those 3 were thought to be trade targets. The Schreiber deal was a little surprising, but it was not a major deal. The prospects given up for O'Neill and Slaten were not major gives.
In short, I could see him trade more than just the 4.
McGuire