Now fully fit, Ziyech has struggled to win over Tuchel, though has started the last two games for Chelsea in the draw with Manchester United and victory over Liverpool. However, for Mulder, Ziyech is a shadow of the player who starred with Ajax before his departure last summer.
Mulder told Ziggo Sport via Voetbalzone: "It is true that if you want to be a real European top player, you should not be dependent on one position.
“It also happens that you come to play under a different trainer and at another club, where not everything is built around you.
“He has to be flexible. His best position is on the right, because there he has the space to give up on Werner, for example. Now he plays like a kind of 'number ten' in the crowd, which he clearly has a bit of trouble with."
Indeed, Mulder says Ziyech looks lost in Tuchel's system - and not only that, but accused his Chelsea teammates of ignoring the Morocco international during games.
He added: "You see him walking around helplessly: he waves his arms and wonders where he should run free and how he can be played in. They sometimes skip Ziyech, and you can see that he is also annoyed by that and that he has difficulty with it."
So far this season, Ziyech has played 23 games across all competitions, scoring twice and creating four assists.
- updated March 8