But if we play a "double pivot" of Ampadu and Stach (assuming we get him), wouldn't that push Longstaff into a No10 position between and ahead of the two (or out wide on the right) ? And no, we didn't play Rothwell, Ampadu, Tanaka and Gruev together, because that's FOUR central midfielders, but we would play three of them. It's hard to see how Stach and Longstaff wouldn't be starters, nor the Captain Ampadu.
Can you explain where we regularly played 3 of those 4 midfielders in the starting line up, as midfielders (ie Ampadu covering at centre half, doesn't count), given that for the majority of games last season we lined up with this formation I think Aaronsson played as the AM, meaning that only DM and CM were available slots for any 2 of our 4 midfielders to occupy. To answer your question of how could we play Ampadu, Longstaff and Stach in midfield, then probably Aaronsson gets dropped and we play a 4 - 3 - 3 formation instead with a double pivot of DM's whilst the third midfielder acts as a box to box or whatever numerous terms are used these days for central midfielder
If we play 4-3-3 (which is really the same as playing 4-1-4-1), with Ampadu, Stach and Longstaff Then you would imagine that Stach plays in the middle, with Longstaff and Ampadu alongside him. That's OK for Longstaff but not for Ampadu who'd be in an "8" role of supporting the attack AND the defence - and that's not his game. Stach would shift sideways to cover Longstaff when he runs forward and by default, we end up with a double pivot with Longstaff ahead of them in a No10 role. IMO those three players don't play well together and it needs to be Ampadu OR Stach, with Longstaff and Tanaka (or a new signing) either side of him.