Dayyani started playing football at fifteen and by the time he was seventeen landed a contract with Aarhus Gymnastik Forening who are currently in the Superliga. In 2003, Dayyani became the youngest player ever to get his debut in the Superliga. At the age of 16 years and 244 days, he succeeded Mads Beierholm"s old record of 16 years and 256 days.
Dayyani had to stop his promising career in 2007 because of injuries and a weak knee.
Dayyani has represented numerous Danish youth teams.