If anyone knows what it's like to underachieve away from the Bundesliga, it's Nuri Sahin.
The 25-year-old first left Dortmund for Real Madrid, before then joining Liverpool on loan. But the midfielder endured a far from productive spell at Anfield and eventually ended up back in Germany.
It is a similar story for Shinji Kagawa.
The Japan international left Dortmund for Manchester United in 2012 in a move that seemed full of promise.
Sir Alex Ferguson failed to get the best out of him, however, while David Moyes got no closer, before Louis van Gaal decided Kagawa was not needed in his side.
As such, the 25-year-old has agreed a move back to the Bundesliga, where he will be reunited with Jurgen Klopp and co.
And Sahin is delighted to have his former team-mate back.
Indeed, Kagawa is 'back home,' where he will hope to challenge for the German league and cup, while also harbouring hopes of repeating their previous heroics in the Champions League.
Dortmund have been drawn in the same group as Arsenal for this season's tournament, although they have already lost in this season's Bundesliga.
Bayer Leverkusen top the standings as the only German side to win two games out of two. Defending champions Bayern Munich have also dropped points, having won once and drawn once.
Was Kagawa wasted at United?