Well, you are one of "but what if?" guys.
You are willing to test/ruin something which is average for something which may turn as better or as a total disaster.
A safe approach is: play the one who is ok (Roberto), since we won a double even with him.
Semedo: play him from time. If he will be good, play him more. If he won't, don't play him too much.
A more radical approach is: play Semedo all the time, and be willing to risk a season in order to see how will he develop.
It could end well: we will find a new Alves.
It could end horrible: we will win less points since we will struggle in attack.
True.
But again, nothing is black and white.
Each player needs time to learn our system.
But some guys are decent from the day 1, some are totally lost.
Examples:
Arthur understands our movement after 3-4 matches.
Ok, people will say: he played in a similar system in Brasil...
Ok, what about Coutinho then?
He was decent from the first match.
And while not perfect, he was let's say 50% good fit and he is improving over time.
With Semedo, he seems like a 10% good fit currently.
So, you see, some players are average in the beginning, and over time they improve to very good once they learn our system.
Others are very poor and their improvement path is way longer since they need to go from horrible to average and then to good.
While Coutinho/Arthur only need to go from average to very good.
For example, you can see right away how Arthur fits better with a team than Vidal.
And Vidal will need way more time to learn our movement.
Ok, he is a different type of a player blah blah, but a point stands.
With some players, you can see right away that they will probably click and fit, and that they won't need THAT much to adapt.
With other players, you see that they will need light years to understand our movements.
Imo, Semedo is one of the guys.
And for me, Dembele also has hints of that problem.
For example, Dembele is more skillfull, but still looks quite lost on a field too often, even after 14 Months here.
Malcom is less skillfull, but whenever he plays, he seems less lost than Dembele, so, he understands our movement better.
On the other hand, Dembele can create more individual magic out of nowhere, which is unrelated to his understanding of our movements.
So, both Malcom&Dembele and Arthur&Vidal will improve over time when they will learn our system.
But some guys are ok from the day 1 and will probably need less time to learn and adapt, while some seem way more lost from the day 1.
And then you have a question: when a guy is totally lost and since he will need way more time to learn and adapt, HOW much time are you willing to give him (also, a team will suffer in that time)?
Further, if a player is a new Messi, then it is more reasonable to give him more time to test him, since a possible reward is very high (Messi, Dembele).
While, if a player doesn't have such a high ceiling (Semedo) and he is lost as hell, and will need a lot of time, then maths is different, risks are higher, a potential reward is lower, so there is less reasons to risk.
More or less, that is exactly what EV is doing.
Semedo is getting some chances.
He isn't improving.
He is lost on a field.
A potentaial reward is questionable.
And so, this is why Roberto plays and Semedo gets soem matches to show whether there is hope for him.
So, EV hasn't closed a door completely for Semedo.
But EV surely won't go "all in" with Semedo and play only him, since a risk of a potential good outcome is way too high.