Dier and Ndombele are literally perfect for a Mourinho two-man midfield, and for some reason they're not playing.
Dier is his (very) poor man's Xabi Alonso while Ndombele is a superior footballer and midfielder to Khedira.
Dier is a bit too clumsy right now, because he got thrust back into the team completely out of the loop. Not sure the others know how to take him as that kind of player yet. But I too believe the CM/DM lineup they have is tailor made for Mourinho. Perfect profiles of players for the midfield generals (Dier/Winks) and dynamic move killers/ball chasers/header winners/tireless runners (NDombele/Sissoko/Wanyama). Alli and maybe even Eriksen removed from participation down low to score freely. It's all there anywhere, but at the back. And even there all he has to do is ensure he renews Alderweireld and buys him a competent younger partner. RB/LB were always relatively reserved for Mourinho so if he channels Aurier's energy while suppressing his lack of wits and moulds Davies into Luke Shaw, they're sorted.
Also could use a better keeper than the broken arm master of flappiness.
2-3 signings and on paper this works quite well.