Sami Aslam is not an established player in the team. He's averaging in the low 30s thus far in his career. He's shown some promise, but so have other players shown promise initially. If he's in poor form (and he looks pretty timid out there), it's not going to do him any favours by sticking with him. Personally I'm not sure he's ever looked the part - his style of play is not one that I get confidence from. He never really looks comfortable to me.
As far as Sharjeel, he was selected because the coach, selectors and captain thought he has potential. If Aslam fails in the second innings, he should get a shot. he can't do much worse and could do a lot better.
He averages in the high 30's, ie above 35. As a Pakistani opener, batting in England, New Zealand and Australia.
'Poor form' is specifically 3 innings so far and will 4 if he fails in the second. In New Zealand and Australia.
Any selection panel that drops a player who has been performing like him after 4 bad innings in New Zealan and Asutralia should themselves be dropped.
Suffice to say Shafiq would long be gone if that kind of run of form counted for anything.
'Look' comfortable' seems a peculiar metric - is it more important than scoring runs? But we could note that in his first England Test he looked so much at ease that a visibly nervous Azhar Ali acknowledged drawing confidence from the young man in constructing his own innings.
As for Sharjeel, I acknowledge that the selectors saw something in him - I don't know about the captain and coach, who seems quite discontent with many of the options given him.
But it is simply a fact that his domestic stats are far from the best on offer. If someone else was to be given a
chance it should rather be Fakhar Zaman, for instance.
So if we believe Sharjeel deserves it most we are taking the position that the selectors always know best. And history does not bear out that assessment.
Lastly, if Sharjeel were to be given a go it should be for 5-6 Tests at least. It is simply nonsensical to drop in
an opener and dump him after one Test. That is not how you build a team. It is how you ruin the confidence
and development of not one player but two.
I think it is telling that no one is advocating this. We all know that Sharjeel is a highly flawed product.