It does matter. The Corey Kluber of 8 months ago (when he was a better bet than Sale will be for next year) is not going to sign here to be one of a bunch of guys competing for a spot in the rotation. If, going into spring training, Sale has a reasonable shot being the 4th best starter, the offseason has gone wrong. They need 4 guys with a higher chance of success than Chris Sale. Maybe 5. The assumption needs to be that he won't be in the rotation.
I believe you're overthinking this one. The point that "The Corey Kluber of 8 months ago (when he was a better bet than Sale will be for next year) is not going to sign here to be one of a bunch of guys competing for a spot in the rotation" is of little relevance. The Sox need two guys to put into spots 1, 2, or 3. They already have one guy in Bello. They need to pick up the other two in trade or free agency, and the guys they get had better be good enough that they have a slot in the top three
locked up.
The point that, "If, going into spring training, Sale has a reasonable shot being the 4th best starter, the offseason has gone wrong" really doesn't mesh with the first point. If two of the guys the Sox have
are demonstrably better than Sale, that increases the chance (if only marginally) that the two pitchers the Sox bring in
will be in competition with the 4th and 5th starters for their roles in the rotation, which, by assumption, you don't want.
Objectively, you would like to know that your rotation is strong enough that Sale won't be a part of it...but the only way you can do that with a strong degree of certainty is to bring in
four more really good pitchers, not two. And that would be overkill. So, it would be ok if Sale were in contention for a spot in the rotation...you'd just rather that two of the guys that you already have are good enough that you don't have to
depend on Sale being in the rotation. That would be a likely disaster, because with all the wear and tear that pitching has inflicted on Sale's body over the years, it's very likely he won't be able to pitch another full season for the rest of his career.