Just play him. Rashford and Martial both need a break or something, both look like they severely lack energy. Also, we can hope that he comes in, is a new entity so we get a bounce, which gets us some results ala Greenwood and Bruno.
Problem we have now is that there will be more pressure on Diallo to perform to the unrealistic expectations of many - introducing a new 18 year old signing would have been perfect during a winning run, doing so on a back of a humiliating loss would be terrible man management and something I hope Ole doesn't do.