Frans is renowned in world football as an assistant to Johan Cruyff and then Louis van Gaal at club sides AFC Ajax, FC Barcelona, FC Bayern Munich and Manchester United, and the Netherlands national team. He has worked with goalkeepers including Edwin van der Sar, Stanley Menzo, Víctor Valdés, Vítor Baía, Pepe Reina, Robert Enke, Łukasz Fabiański, Thomas Kraft, Michel Vorm and David de Gea.