Tbh at this stage I'd give Maitland-Niles a go at CM rather than Jack. The guy has the physical and technical attributes to play in the role and eventually go on to be a lot better than Jack is - the club really rate him highly. I'd love for him to start getting 10 mins at the end of most games instead of a Jack or an Elneny tbh.
The problem with Jack is that given that's unlikely going to sign a new contract (due to the way he feels he's been unrespected by the club) so there's not point really developing him further at this point. If we play him and he recaptures some of his form, it's only ultimately going to benefit another club.