With Mourinho, Griezmann. Every team that he built played 4-2-3-1 and I think that Griezmann would be perfect for that role (hard worker, scores a ton of goals, fools defenses with ease etc).In a hypothetical scenario, would everyone prefer Griezmann, and continue to play a 4-2-3-1, or signing a right sided top class central midfielder (Koke, Saul, whoever you want within reach) to play Pogba at his best in a looser role in a three man midfield?
With some other manager (Pep, I am looking at you) then a good right sided central midfielder to complement Pogba in a 4-3-3.