Covid disruptions to the Chelsea squad meant the winger started the last two league games for the club, both of which they failed to win.
When everyone is fit, Ziyech is not a certain starter at Chelsea and he has been heavily linked with a move away from Stamford Bridge in the January transfer window.
Dortmund have their eyes on the Moroccan and want to take him to the Westfalenstadion next month.
But according to German daily Bild, they have to move on a few players before they can try and sign Ziyech next month.
The Bundesliga giants need to sell some of their high earners in order to make space on their wage bill for Ziyech.
Dortmund are considering selling Roman Burki and sending Reinier Jesus back to Real Madrid early from his loan stint.
The Chelsea star is very much on their radar but for the moment, they will have to find space on their wage bill for him.
Barcelona have also identified the Moroccan as an alternative target if they fail to sign Ferran Torres from Manchester City next month.
