Borussia Dortmund long-serving defender Marcel Schmelzer will end his football career after the current season, he said on Instagram on Thursday. “Unfortunately, injuries have set me back time and again over the last two years,” the 34-year-old player said. “In this context, I would like to thank Dortmund for allowing me to complete my rehab here. I don’t know what’s coming yet. But I’m looking forward to the challenges.” Schmelzer moved from Magdeburg youth academy to Dortmund’s under-19 team in 2005. Since 2008, he played 367 games for the first squad, winning the Bundesliga twice and the Ge…