One of the quickest things to matter in a new season is going to be YoY velocity changes. This is stupid early, but here's every pitcher on the team that's thrown so far.
Pitcher - '23 velo / '22 velo
Stroman - 91.7 / 92.9
Steele - 92.3 / 92.4
Taillon - 94.3 / 94.1
Assad - 94.3 / 93.0
Fulmer - 95.1 / 94.3
Thompson - 93.4 / 93.8
Leiter - 90.9 / 91.2
Boxberger - 93.0 / 92.8
Alzolay - 96.8 / 95.0
Merryweather - 96.4 / 97.4
Rucker - 95.5 / 94.9
Alzolay is the clearest positive. If he's going to be sitting 97 permanently he will be the permanent closer within a few weeks. Assad too, though his coming out party already happened in the WBC. One other I'll note though is Steele, his velo being flat while pitching in those conditions might mean he's really added some juice to his fastball.
Stroman and Merryweather are the only guys down noticeably. I don't love Stroman being down, because he got warmed up for the WBC I wouldn't expect him to e.g. be going through dead-arm. Merryweather hopefully it was a one-off, because if he's not throwing absolute gas he shouldn't be long for the roster.