Sport's highest court has doubled Hamburg defender Mario Vuskovic's doping ban from two to four years, the Court of Arbitration for Sport announced on Tuesday.
The Croatian player tested positive for the banned blood-booster EPO at a training session for his German second division side in September 2022.
He was initially handed a two-year suspension last year by the German league's disciplinary panel.
Tuesday's verdict means the 22-year-old will be ineligible to play until November 2026.
CAS explained in its ruling Vuskovic "did not submit any mitigating factors that could be taken into account to reduce the four-year period of ineligibility".
It consequently dismissed Vuskovic's appeal against the ban, and at the same time upheld appeals by the Wold Anti-Doping Agency and Germany's doping watchdog NADA, who had both sought the ban be doubled.