Now 24, the talented midfielder has spent much of his time as a senior player away from his parent club on-loan. Before his German move, Baker spent time with Sheffield Wednesday, Milton Keynes Dons, Vitesse, Middlesbrough, Leeds United and Reading between 2015 and this year.
For his part, Pfannenstiel is pleased with their addition, admitting he'd been following the midfielder since his time with Vitesse. It was in Arnhem where Baker spent two seasons, making 64 appearances for 15 goals and eight assists.
Pfannenstiel told the club's website, "He brings everything with what you need as a central midfielder.
"Baker is strong, dynamic and dangerous.
"I am sure that he will set new standards in the Bundesliga and will do well for our creative game."
Pfannenstiel took charge of Fortuna only in December, leaving Hoffenheim after seven years with the club where he served in a series of roles, including as scout and as Head of International Relations.
This window is the former goalkeeper's first summer market in the role of sporting director.
- updated July 29