We can discuss all we want re rotation, but the fact is that Sensi & Barella are injured and even Gagliardini may not be ready to start yet. Which means we have no options in the midfield - its Brozo, Valero and Vecino. This is what we got, and to make sure we win against SPAL we need to start our best available players in all other positions.
We have done very well to cope with our injury crisis so far, but also have been helped with the schedule of "easier" games in Serie A. My bigger worry is the next 6 games after SPAL, its Roma (h), Barcelona (h), Fiorentina (a), Genoa (h), Napoli (a), Atalanta (h). This is where our season could quickly turn pear shaped, specially with all these injuries. Hopefully by the time of the Napoli game, we will have Barella, Sensi and Sanchez fully fit, and maybe if Marotta has any sense, we will have 2 new quality players signed up as soon as the window opens.
Even then, negotiating Roma-Barca-Fiorentina in 9 days without Barella, Sensi and Sanchez is cause for serious concern. Realistically I expect some points to be dropped, but I worry that the team's mentality/spirit will take a hit if we go out of CL & Scudetto contention in the same week.