So all we need to do is find the greatest footballer of all time and one of the best forwards of his generation for the £40-45m we'll have remaining in this season's transfer budget. No biggy.
United don't need to replace him all at once. There's always going to be growing pains. Goalkeeping and forward line will be examined this year and next year.
Develop the team as best as possible and replace the players and positions as it comes.
Midfield and defense is being identified this season. Along with a wide forward, hence being linking with Antony.
Martial and Ronaldo will be replaced individually and collectively within the next couple months or 18 months. This is the surgery that Rangnick and many others foresaw. But it's not all going to be done within 2 months. Ronaldo leaving is just a major piece, but a piece that was bound to happen soon. Soon just so happens to be now, once/if a suitable offer and club submit.