That is a fair question. I think you have to look at the pitching staff this way for October.
1. Sale. You expect to get 6+ good innings from him. If you don't, you're not winning much of anything.
2/3. Porcello and Price. You'd like to get 6 innings - but you're really planning for two trips through the order.
4. Eovaldi. You want to get 2 trips through the order, but you plan for 1.
5-6. Rodriguez, Johnson as multi-inning bridges. They are there to back up a bad performance. More helpfully, you'd like to have him ready for being able to get through the order once and then on to the 1-inning dudes.
7. Kimbrel is the closer
8-11. Barnes, Kelly, Velasquez and Workman
Now looking at the position players
OF: Benintendi, Betts, Bradley, Martinez
SS: Bogaerts
2B: Kinsler, Holt
1B: Moreland, Pierce
3B: Devers, Nunez
C: Leon, Vaszquez/Swihart
So we have 13 position players. The question becomes whether you want to carry another pitcher - or do you add a 14th position player. Do you make a trade for a Quinton Berry designated PR sort? Or do you try to find another outfielder for defensive flexibility? Would you rather add, say, Rusney Castillo in pursuit of both goals?