According to reporter Florian Plettenberg's report, the release clause in Guirassy's contract only applies to a few top clubs.

Serhou Guirassy is one to watch for the summer, as he could leave Borussia Dortmund.
29 y/o top striker is understood to have a release clause that should be at “only” around €50 million. It applies to seven top clubs: Real Madrid, Barcelona, Manchester City, Liverpool, Chelsea, Arsenal and Manchester United.
