Im more worried by some of his decisions that are not affected by "settling in"
Today we went through a 5 minute spell at the end of the first half were we could have conceded 3 or 4. The defence completely fell apart and went in to panic mode, when this happens no matter of settling in an experienced player should know to try and get control of the game, but Klaassen was arguably guilty of giving spurs 2 of those chances before half time. One of them he had a simple pass on the left and couldn't complete it and then one on the right which he tried to fancy mid air back heel it and the ball went the opposite way of our player.
Yes he's going to take time to settle but he has to stop trying to play the Ajax way, it will not work in our system (or lack of system) and the success rate from deeper lying midfielders moving from Holland to England is incredibly poor because the football is so different.
I won't write the lad off because we've invested a fair bit in him and it would be wrong to say a player who only a few months ago was captaining a side in the europa league final isn't good enough to make the grade, but right at this moment he shouldn't be near the team against anyone capable of finishing 10th or above.
For the people who back him religiously and believe wholeheartedly it's a case of "settling in" from a poor league bear in mind that was Sanchez' first game in English football from the exact same system as Klaassen last season so it might not be a case of him needing time he might just not be good enough.