Replace a bench warmer by another one lol.
Still only if Trincao and Dembele leave or coach must rate him higher than both.
What role do you expect him to have if he stays? He'll obviously start as a squad player but could earn more minutes in time if he'll convince Koeman like Pedri (who was also supposed to go on loan at first) or Mingueza (who nobody really expected would get close to the first team this year). He can be both a 5th (or more likely 6th) midfielder and 3rd string RW which is beter than being a 4th choice AMC (a position we don't really use but if we do we have Messi, Griezmann and possibly also Pedri who are all clearly better players) only like Riqui.
I think Collado's decision will depend on what system we'll primarily use and what will happen with Dembele and/or Trincao. He's one of my favorite Barca B players in recent years but I still believe Trincao has a better upside so I hope we won't give up on him. But if we'll continue to play 3-5-2 there is no real position for him. So maybe send him on loan. If he'd do well there we can either get him back or sell him next year for more than what we'd probably get this summer after not playing much. And keep Collado around to see what he can do next season then decide about his future.
We should have a more "normal" preseason this summer with 5-6 friendlies so Koeman could have a good look at some players with uncertain future. Especially with most starters probably joining preseason lately due to Euro and Copa America likes of Collado should do their best to convince Koeman. But if he'll decide those players are unlikely to get minutes then I hope they'll be smart enough to listen to him an go on loan because it's unlikely he'll change his mind.
