Look, obviously Trevor Bauer should be the answer, but the Sox aren't in that market. For my two cents, when I look at this rotation as it stands today there are a whole of of innings and starts to fill. We know Kopech probably isn't starting this season with the big team. It really sounds like they want Crochet working out of the pen. So how do you fill those innings?
For my two cents, my #1 goal is to not do anything that endangers the depth and future pieces we have coming through the system. We already did it with Dunning and Lynn. Hopefully Lynn extends to fix another future hole in the pen, but until they, the pitching should be mostly off limits. Maybe a Steiver whose timing is blocked by the guys who are already ahead of him, but for the most part, pitching should be off limits.
#2 hopefully we are looking at the free agent market. Keep in mind with the injury risks, if they aren't starting, then you are dropping into the minors to cover their starts. So if your bring in a Paxton or Richards, sure you get some great starts, but then you also get Reynaldo Lopez, Jon Stiever, and company doing a lot of other starts. The stability of knowing that you are pretty sure about getting a certain guy, and knowing that he is going to give you six innings every five days allows you to set your pen, not overextend those guys, and have them ready to go when you need them.
#3, again while it would be nice to be getting a top flight guy to fill in back of the rotation, if you can't, it isn't the worst thing, because you are going to be running one of the best offenses in baseball out on the field every day, so if you have to win some games 7-5, so be it. You are OK with that.
#4, while we want the Sox to spend, they are obviously being safe and conservative with the budget. Assuming this season isn't a worst case scenario, hopefully a budget conscious move allows them to make another move at the deadline, if needed.
Realistically, Jose Quintana fits this resume. He is also a guy you already know, and he seemed to fit into the White Sox just fine before, so there isn't a real feel that he wouldn't now.