Marin moved to Italy at age 18, when Sassuolo transferred him from his hometown side ASU Politehnica Timișoara. After three years under contract with the Neroverdi, during which he was loaned out to Catanzaro and Pisa, he decided to sign for the latter club on a permanent basis.
In late August 2016, Marin transferred abroad to Sassuolo after having trained in Italy for one month. He signed a four-year contract after turning 18[4] and spent his first season with the Primavera side. For the 2017–18 campaign, he agreed to a loan deal with Catanzaro in the Serie C.
Pisa
Marin was again loaned out by Sassuolo for the 2018–19 season, joining Pisa with which he achieved promotion to the Serie B. On 31 July 2019, he returned to the Arena Garibaldi on a full transfer.[5] Marin scored his first career goal on 3 July 2020, in a 2–0 league win over Cittadella.[6]
During early 2021, it was reported that several teams from the Serie A were monitoring Marin,[7] as well as two of the title contenders from his native country—CFR Cluj and FCSB.[8] Nothing came of it however, and on 20 October 2021 he signed a contract extension with Pisa which would run until 2025.[9]
On 28 August 2022, Marin made his 100th Serie B appearance and also wore the captain armband in a 0–1 loss to Genoa.[10] In October 2023, he played his 185th game for Pisa, becoming the foreign player with the most appearances in all competitions for the club.[11]
Marin stated that his parents struggled financially to support his youth football practice, so he used the first money he earned in Italy to build a house for them.[21]