If we sign Ronaldo we will have either no money or little money for a midfielder left (assuming no big player gets sold, with the exception of maybe Higuain).
Meyer for 'free', Wilshere for 'free' or maybe Vidal in a delayed deal like the Benatia or Costa deals could be options.
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We need both Cancelo and Alex Sandro to feed Ronaldo with chances to break all the records there are in Italy.
You can't sign Ronaldo and expect him to have to play with Darmian instead of Marcelo. Alex Sandro needs to stay, Darmian should only be a back-up option, if he signs with the club.