According to Germanijak, left back Marcel Heister has been signed by NK Osijek from Istra 1961. The club confirmed that Heister's contract is for one year with an option for an additional season. Heister stated that he was presented with Osijek's vision after contact was initiated and made a quick decision to join upon learning of their interest. He also mentioned having other options but selected Osijek due to the ability to remain in Croatia and his view of it as a big club. Kenneth Zandvliet, Osijek's sporting director, commented on Heister's experience and qualities and expressed happiness regarding the signing.

The Croatian top-flight club Osijek announced the arrival of Marcel Heister, a former Ferencváros and Videoton footballer who had already spent the past two seasons in Croatia.

Osijek has signed a replacement for Roko Jurišić, who is expected to complete a transfer to Aris in Greece. The club has brought in Marcel Heister, a 33-year-old German and Croatian left back, as a free agent with no transfer fee. Heister's contract with Istra 1961, where he spent the previous two seasons, expired this summer. The experienced defender is expected to fill the left-back position following the departure of Jurišić and the contract expiration of Borna Barišić. Transfermarkt states his current market value is €200k.