New Borussia Dortmund coach Nuri Sahin began the job in earnest on Wednesday when 15 players reported for diagnostics tests. Sahin, who was already assistant manager, took over from Edin Terzic after his resignation following the painful Champions League final defeat to Real Madrid. The European Championship players and US international Giovanni Reyna, who played in the Copa América, will join up with Dortmund later in the month. While Dortmund’s non-internationals arrived at their training base, the Dutch national team was completing their final warm-up session before the European Championshi…