Yana da shekaru 16 a watan Maris na shekara ta 2011, bayan da ya burge a cikin wani kwarewa a Brussels. A karshen kakar wasa ta 2012-13, mai kula da United Sir Alex Ferguson ya inganta Januzaj zuwa tawagar farko kuma an yi masa rajista tare da lambar lambar 44; bai yi wasa ba a cikin sauran kakar, amma ya kasance mai maye gurbin da ba a yi amfani da shi ba a wasan karshe na kakar wasa zuwa West Bromwich Albion. Domin wasan da ya yi a kakar wasa, Januzaj ya lashe kyautar Danzil Haroun Reserve Team Player na shekara ta 2013. An hada shi a cikin tawagar farko na 2013-14 na kakar wasa ta Asiya kuma ya zira kwallaye a wasan karshe na yawon shakatawa da kungiyar Hong Kong Kitchee.
Ƙungiyar kwallon kafa ta Brussels