 He was relieved of his duties in 2015.He was later put in charge of the Denmark national under-21 team, before being appointed head coach of Brøndby in June 2019, replacing Alexander Zorniger.Frederiksen is noted for his exceptional work with young talents, developing players such as Andreas Christensen, Andreas Bjelland, Yussuf Poulsen and Christian Nørgaard in Lyngby, and Martin Braithwaite at Esbjerg.