I wouldn't be surprised actually if the club bring in a few loan signings from overseas before the window shuts, just to pad out the squad without committing a new manager to players he may not want.
I think if he was injured in a match like Eduardo was it would be the case with Delph, but it was a training injury and as long as he is ok physically I think mentally he will be fine.
Relax - I was just being facetious
I actually think it's a bit harsh though to cite Delf's pre-season as a reason to leave him out when he was off representing England.
Hopefully though it will be just a little kick in the bum to get him extra motivated to put the scoring boots on.
I'd say the situation is that they will look at all the available candidates including K-Mac. However they would be nuts if they just decide to hand MacDonald the job without closely looking at the other candidates, whoever they may be.