Klopp says his former BVB star is wasting his talent.
"My heart breaks. Really, I have tears in my eyes.
"Central midfield is Shinji's best role. He's an offensive midfielder with one of the best noses for goal I ever saw.
"But for most Japanese people it means more to play for Man United than Dortmund. We cried for 20 minutes, in each others' arms, when he left."