I don't think there is a medically significant reason to differentiate a start in Worcester and a start in Fenway at this point in Sale's recovery. I also think he is deep enough into his pitch count and arsenal and stuff that his in game approach wouldn't be different from a stepping stone, what I'm working on perspective.
So the decision on where he makes his next appearance(s) comes down to a number of factors:
1) The chances of him performing in the game (win % and innings before the bullpen) compared to the replacement option
2) The psychological impact of getting him back for the team (and similarly the difference in getting him back at 90% vs 95% or whatever if he were to return an extra start early, and his return isn't as dominant as it could be later)
3) The psychology of a pitcher returning from a major injury, who has never known how to back off, come out of a game an inning early, and is a ferocious competitor.
If we were operating robots and were focused only on #1 and not on 2 and 3, I would definitely have opted to bring him back sooner, let him have an opener game, pitch 3 or 4 with a piggy back, and pitch 5 or 6 when he can, as I think he is good enough to add real value over the bottom of our rotation before he is 100% locked in and ready to strike out 12 in 7 shutout innings. Over and over my rational analytic self things that his starts in the minors are starting to be a luxury that reduces our chances of winning the division.
But I think the FO and Cora are likely much more dialed in to the impacts of 2 and 3, and that rehabbing on the job, even if it is more technical value than innings from our #5, likely would have offsetting impacts harder to measure, and they want to be patient and get him back to 100% where they don't need the deflating moment of pulling him after four innings down 4-1. So while Analytically I think moving some of his minor league innings to the major leagues would improve our team performance, I respect the delicate balance and am excited to tune in whenever he is ready to deal.