He is on the books of Eilenburg and wears shirt number 17. His main role on the pitch is Forward. His stronger foot is Right. His estimated market valuation currently stands at 50K €.

His latest transfer saw him join Eilenburg from Lichtenberg 47 via on 2025-07-13.

During the German Regionalliga 2025-2026 campaign, J.Mattmüller made 20 appearances, scoring 3 goals and adding 0 assists. He averaged 0.2 goals per match from 0 shots, with 0 on target.