Kammala wannan magana: Grün ya fara aikinsa tare da Anderlecht a Belgium, inda ya shafe shekaru takwas, ya lashe gasar cin kofin UEFA a
1983, kazalika da jerin sunayen rukuni na farko na Belgian tsakanin 1984 da 1987, a tsakanin sauran kofuna; ya kuma kai wasan karshe na gasar cin kofin UEFA tare da kulob din a shekarar 1984, inda suka yi rashin nasara a hannun Tottenham na Ingila. Grün ya koma kulob din Parma na Italiya a shekarar 1990. A lokacin da yake tare da kulob din, ya kafa kansa a matsayin daya daga cikin 'yan wasan da suka fi dacewa a Serie A, ya lashe Coppa Italia a shekarar 1992, da kuma gasar cin kofin zakarun Turai a shekarar 1993 a karkashin kocin Nevio Scala. Bayan jerin gwagwarmayar raunin da ya faru a lokacin kakar wasa ta 1993-94, duk da haka, ya koma tsohon kulob dinsa a 1994. A cikin 1996, ya sake komawa Italiya, don buga wasa a Reggiana; duk da haka, kulob din bai sake biyan shi ba tsakanin Fabrairu da Mayu 1997, kuma ya yi ritaya a ƙarshen kakar wasa ta 1996-97.