Ku dhammaystir weedha soo socota: Ka soo koraya Michigan, Joshua wuxuu u ciyaaray hockey-ka yar ee kooxda Honeybaked U16 midget waxaana lagu casuumay Xero Qiimeynta Kooxda Xulka Qaranka ee USA Hockey Select. Ka dib xilli ciyaareedkii 2011-12, Joshua waxaa qortay kooxda Sioux Falls Stampede wareegga saddexaad ee United States Hockey League (USHL). Ka dib markii uu kala qaybiyay xilli ciyaareedkii 2012-13 ee u dhexeeya Honeybaked iyo USHL, Joshua waxaa loo qoray 156aad guud ahaan Plymouth Whalers inta lagu gudajiray Xulashada Horyaalka Hockey ee Ontario. In kasta oo la soo saaray, wuxuu sii waday inuu ka ciyaaro OHL xilli ciyaareedkii 2013-14 waxaana uu kaalinta 157aad ka galay guud ahaan ciyaartoyda Waqooyiga Ameerika ee NHL Central Scouting Bureau. Joshua waxaa ugu danbeyntii lagu soo xulay wareega shanaad, oo ahaa kii 128-aad,
2014 NHL Entry Draft ee Toronto Maple Leafs. ma uusan ogeyn in lasoo xulay ilaa uu ka helay taleefan ka socday maamulka Toronto isagoo saaran gaariga Ka dib markii uu qoray Joshua, agaasimaha indha indheynta hiwaayadda ee Leafs Dave Morrison wuxuu si aad ah uga hadlay isaga ciyaaryahan ahaan, isagoo leh: "Wuxuu dheer yahay, aad ayuu u ciyaaraa waxaanan aragnay xoogaa iftiin ah oo xirfad fiican leh dhamaadka sanadka. Tababarihiisu ma sheegi karaan waxyaabo fiican oo ku filan isaga. Waa ciyaaryahan aad u dadaal badan oo ka mid ah sagaalka ciyaaryahan ee ugu sareeya". Joshua wuxuu laba xilli ciyaareed oo buuxa la qaatay Stampede, oo uu ka caawiyay inay ku guuleystaan horyaalka 2015 Clark Cup.