The Dutchman, one of our greatest all-time goalscorers, will work with the coaching team to help plot a route into the Carabao Cup quarter-finals, following Erik ten Hag's departure on Monday.
Ruud is guaranteed a rousing ovation from the Old Trafford faithful but the focus will, of course, be very much on defeating the Foxes, on the back of a convincing win over Barnsley in our previous outing in this season's competition.
It will be interesting to see which line-up Ruud selects for the 19:45 GMT kick-off, with checks likely to take place on Noussair Mazraoui, after he came off during the 2-1 defeat at West Ham United.