On 21 May 2017, Muslija made his debut as professional footballer in a 2–1 away defeat against Eintracht Braunschweig after coming on as a substitute in the 70th minute in place of Kai Luibrand.[2] Three days after the debut, he signed a two-year professional contract with Karlsruher SC.[3] On 9 November 2017, Muslija extended his contract prematurely until 2021.[4]
Hannover 96
On 31 August 2018, Muslija in last day of the 2018 summer transfer window signed a four-year contract with Bundesliga club Hannover 96.[5] Hannover 96 reportedly paid a €2 million transfer fee.[6] His debut with Hannover 96 came on 30 September in Matchday 6 of 2018–19 Bundesliga against Eintracht Frankfurt after coming on as a substitute in the 69th minute in place of Julian Korb.[7]
SC Paderborn
On 2 January 2022, Muslija signed a one-and-a-half-year contract with 2. Bundesliga club SC Paderborn and received squad number 30.[8] Thirteen days later, he made his debut in a 2–1 away win against 1. FC Nürnberg after being named in the starting line-up.[9] Seven days after debut, Muslija scored his first goals for SC Paderborn in his second appearance for the club in a 3–4 home defeat over Werder Bremen in 2. Bundesliga.[10]
^Dankert, René (31 August 2018). "Muslija verlässt den KSC" [Muslija leaves the KSC]. Badischen Neusten Nachrichten (in German). Archived from the original on 9 November 2019. Retrieved 22 June 2019.
^"Spielanalyse/Eintracht Frankfurt–Hannover 96 4:1" [Match analysis/Eintracht Frankfurt–Hannover 96 4:1] (in German). Kicker. 30 September 2018. Die Hannoveraner, bei denen Muslija noch zu seinem Bundesliga-Debüt kam, blieben zwar bemüht, allerdings auch weiterhin völlig harmlos