Agree with Milo, a rotated well prepared team, would be best on Thursday.
Otherwise we play Swansea with a tired side, and I think we'd be relying on the rub of the green to get a win. Poch and team need to earn their money now at the business end of the the season. A hard working rotated team will have a good chance at home, and if we lose, we can focus 100% on the league which will help us massively.
If our rotated team progress, then we will be using our squad to good effect. But will Poch feel pressure to play the big guns on Thursday and again Sunday?
Of our next four games, Swansea is by far the weakest side. We might start a strong side, but should not need to play one for the full 90 minutes.
The question is, do we start strong against Fiorentina and try to rest players when (if) it's in the box or ride out the first hour with a slightly weaker side before (hopefully) finishing them off?
All we need is a clean sheet, so would start the trio of Alderweireld - Wimmer - Dier. FBs will be Trippier and Davies.