Marcin began his youth career with clubs in his native Poland, with trials at Barcelona and Chelsea highlighting his early promise.
He signed for the West Londoners in 2016 and climbed through the ranks at their prestigious Cobham academy.
The stopper climbed the ranks with the Blues and featured in the UEFA Youth League.
He was called up to the senior team on a handful of occasions under Maurizio Sarri before moving on to join PSG as a 19-year-old on a pre-contract agreement in July 2019.
Marcin spent time away from Les Parisiens on loan with Cartagena in the Spanish Segunda Division and Chateauroux in the French second tier.
He would go on to make two senior appearances for PSG before being loaned to league rivals Nice, with an option to buy, for his first competitive taste of senior football in a top flight.
Marcin signed permanently with NIce at the start of the 2022-23 season and will be looking to build on a successful start to the new campaign, which has seen him claim the number one spot at the Allianz Riviera.
He was also named in the senior Poland national team squad for the first time this year after being called up for their Euro 2024 qualifying clashes against the Faroe Islands and Albania.