The Blues and the Dutch giants announced a deal this week for the Moroccan to move to London this summer, with the fee potentially rising to £36.5m (€44m) if performance-related add-ons are met.
The Ajax star has overcome adversity after growing up in the small Dutch town Dronten, where is mother brought up nine children.
But after initially breaking through at Heerenveen, before moves to Twente and Ajax, Ziyech credits his time playing on the streets for enabling him to make it as a professional.
“All I did was play five-a-side on the streets with my big brothers and other big lads. I was always the smallest kid,” Ziyech is quoted as saying in the Mirror.
“You had to prove that you could play – and I think I managed to show them I could play well. I learnt how to take kicks and knocks.
“Some big lads would take into account that I was still a small boy, but others did not give a monkey’s. They would go in hard. But it never bothered me. In fact, I did not care about anything in the world. As long as I could be out there every day.”
Ziyech committed to Ajax at the end of last season following their fairy tale run to the Champions League semi-finals.
After signing a new deal last summer with the likes of Frenkie De Jong and Matthijs De Ligt opting to move on, the 26-year-old has continued to shine at the heart of Erik ten Hag’s side.
Ziyech has eight goals and 21 assists this season and will hope to help clinch another Eredivisie title – with AZ their closest rivals, three points back – and go deep in the Europa League, with Getafe their opponents in the last 32, before his next challenge at Stamford Bridge.