Been quietly saying this for awhile now but I think Alzolay breaks out in a big way this year. To start with he's sitting on 9.86 k/9 on the season over 21.0 IP. When you add in his previous stints in the majors that another 42 k's with his current 23 over in 54.2 IP which breaks down to an absurd 10.7 k/9. For reference here, if we go back to 2019 for the last full season the list of starters with better K/9 are Cole(13.82), Scherzer(12.69), Robbie Ray(12.13), Justin Verlander(12.11), Giolito(11.62), Matthew Boyd(11.56), Yu Darvish(11.54), deGrom(11.25), Charlie Morton(11.10), Bieber(10.89), and Strasburg(10.81). In other words, your basically looking at the top 5 cy young candidates for both leagues with that range of K/9.
What's really hurt him so far in his major league career has been his 4.99 BB/9. That ain't it chief. However, that historically hasn't been an issue for him. In the minors he only walked people at 2.7 bb/9 rate and typically that is something that translates to the majors.
In terms of HR prevention, he's been a little worse than league average at 1.29 but again in the minors he was pretty great with that at 0.8 HR/9. Granted that is an area you would expect to see a rise from level of competition but on the other hand, that's also something young pitchers are going to struggle with early on and learn how to pitch around MLB batters.
The biggest concern for him honestly is probably durability. Can he go ~200 innings? If he can, Alzolay statistically looks like a monster prospect. I'm not even trying to gas him up that much I just think he's being slept on quite a bit by people. Him adding those pitches last year also makes him way more interesting with a 5 pitch mix.