It doesnt matter why a player was brought in and regardless of that he was given that starters role and needs to play well enough to maintain it.
There is almost no top manager that will continue to have a players as starter just because they were bought for that reason regardless of how they play. It doesnt matter why he came it matters if he can justify that reason.
Never said anything about long term solution other than the best RB should play and if Semedo proves to be the better RB and long term solution then he will get that spot.
If Semedo is as good as you say he will prove it and is getting a lot of chances to. For now Roberto has been better.
Obviously I highly respect your opinion, even if I do not agree with it, so in defense of my own point of view, let me just quickly state a few generic things:
1. Coaches, who always want to play those players having been in good or best form, are actually doomed, because the coach's well thought out system will always suffer, if xyz player "must" play, because he has proven to be in good shape and form. A well playing team is always better than 1 or 2 individuals playing outstandingly.
2. That's why a wise coach breaks up his team only, if there is an urgent need to do so, injuries happened, or a specific player is needed for a specific task at the next match.
3. The coach, who is looking, searching for the replacement of a player who played badly 2-3-4 games in a row, is a careless and bad coach, because before all he needs to adjudicate if the player is a good one in bad form, or a mediocre one, being in very good form. The good coach will play the better player in bad form at important games, because he is aware of his qualities - and will occasionally play the mediocre one in good form, usually against easier opponents. (Hope you don't want me to come up with thousands of examples of this...)
4. So will Messi, Suarez, Ronaldo, Neymar, Cavani or anyone else for that matter play when they are in bad form? Yes, because the coach still trusts their known and proven qualities. Of course it is an entirely different matter if the player is tired and needs rest (either for physical or mental reasons).
5. The spectators, and the press often declare that such and such TEAM is in bad form, we all know that titles... But is it statistically or humanly possible that 15-16 players are in bad form in a single team, at the same time? No way, it simply cannot happen (unless they played too many games, traveled too much and stuff like that), but if they are NOT tired, just being in bad form, it ALWAYS means that the system, the tactics, the approach, the coach's access, his approximation or the approach-forcing system is bad, changed, or simply did not adapt to the present circumstances.
Thus, in a case like the team playing badly, the wise coach adheres to his core players, maybe makes minor changes, whereas a bad coach immediately starts to turn the entire team upside down, and starts trying out newer and newer players.
6. The other important factor is that when we call a particular team being in "bad form", it often happens that they aren't in worse form than previously, it is that they aren't LUCKY enough at games or games in a row. When a defender slips while trying to reach an opponent, when the ball goes out from the woodwork, instead of going in, when a referee is biassed, etc. these factors highly contribute to any result and it is simply the unknown factor, namely: luck. Because we all know that a good team simultaneously needs to be lucky as well... Luck is an integral part of the game, like it or not...
7. If circumstances allow, the wise coach has to build a team, according to the two major factors: -the available material of players, -and his own apprehension or his own balked desires. It may take 1-2-3 years to build that ideal team of his up, so results are rarely instant, it takes time and a tremendous amount of work.
8. So the wise coach - while constantly trying to give acceptable results to the present - ALWAYS tries to build the team for the future, and this is where it is questionable if he abides to players playing well, but at unfamiliar posts or with rapidly changing teammates in the formation. A "born" midfielder who is in very good form, might also play quite well as a defender, but trying to play him there, just because he plays well, is a RISK, a risk that clever coaches rarely or never take (unless the half of the team is in bed with injuries).
9. So from the coach's angle, he should see, imagine, predict, etc. how a player will play at a given post in 1-2 years from now, and therefore it is NOT the highest factor in his considerations, if another player accomplishes the task better - right now.
Therefore he has to cultivate, form, animate, assure and bolden the player in his long term plans, rather than just simply judging who plays more or less better in a period of a few weeks or months.
10. So if Valverde - just as an example to the generic notion here - believes that Roberto is the solution (the long term one) then he is doing it right. But in case he believes that Semedo can or will become the "new Alves" for this team (as many believed), then he is doing it wrong, because a 25 yrs old defender will not get better by fighting for his place in his new club, he will sooner or later definitely lose necessary mental strength and other factors, needed to play better, whereas Roberto could be a very useful member of the team elsewhere on the field...
As a result of the present status and tendencies regarding these two, you will get two frustrated players, instead of none...
