Borussia Dortmund slumped to a 4-2 loss at promoted Holstein Kiel on Tuesday, piling the pressure on coach Nuri Sahin after the team’s worst opening half to the Bundesliga for 10 years. After conceding three goals in the first half, the visitors clawed back two in the second through Gio Reyna and Jamie Gittens, but they were unable to capitalize on Kiel substitute Lewis Holtby’s late sending off in the 86th minute for a challenge from behind on Felix Nmecha. Instead, with Dortmund goalkeeper Gregor Kobel in the opposition box for a corner in stoppage time, Fiete Arp sealed Kiel’s win by shooting the ball into the unguarded net on a counterattack.