#2 Antoine Griezmann for Alexis Sanchez

This is another big one. A support striker for another, only the other could also play in the wings. Alexis Sanchez's move to Manchester United has not been good by any means. Be it the goals, or assists, or fan support, or good morale on the pitch, everything is missing in Sanchez. And it is not because he does not have the ability, some times it just doesn't work out.
Ole Gunnar Solskjaer's appointment is another reason why Alexis' time at United may just be up. He hasn't featured much under the Norwegian and is not likely to in the future too. With the horror performances that he has put up at the club, no one would want him to stay too. On the contrary, the huge wage bill for him could cost the club a player like David de Gea, a man who has been winning the Matt Busby Award for fun in recent past.
On the other hand, Ole is trying to freshen things up and would like a person like Griezmann in his team. He is a good player around whom the attack can revolve around much more than it would with Lukaku up front. Griezmann can also experiment in the false-9 role and it won't be bad as he is used to playing as a La Liga support striker. Maybe there is an argument as to why go for Griezmann when the front three is looking set. But if you ask me, one Griezmann in exchange for one Alexis Sanchez, I will take that on any hour of the day.
So why should Sanchez go or what benefit does Atletico have? In any case, Griezmann is not staying for sure at the club. The other striker options left are Morata and Costa. Costa has been in terrible touch. Other than them, Kalinic and Angel Correa are the options. Out of all these names, Correa is the only name who will suit a support striker in a 4-4-2 as Atleti plays.
Alexis Sanchez is an amazing player. Better than all the options available on the table for Atletico if Griezmann leaves. He has also done pretty well in La Liga during his time at FC Barcelona. Atletico could be the place where he turns things around. He can play as striker, support striker and also in the wings if required.
Griezmann has a very high release clause so Manchester has to give an extra maybe 60 million along with Alexis. But it will be good considering the wage bill that they save on Alexis if he stays and also the 100 million they have to pay otherwise.