Whakaotihia te rerenga e whai ake nei: I te tipu ake i Michigan, i takaro a Joshua i te hockey rangatahi mo te roopu midget Honeybaked U16 a i tonoa ia ki te USA Hockey Select National Team Evaluation Camp. Whai muri i te tau 2011-12 o te tau, i tohua a Joshua e te Sioux Falls Stampede i te rauna tuatoru o te United States Hockey League (USHL). Whai muri i te wehe i te tau 2012/13 i waenga i a Honeybaked me te USHL, i tohua a Joshua ki te 156th katoa na te Plymouth Whalers i te wa o te Whiriwhiringa Tuatahi o te Rōpū Hockey o Ontario. Ahakoa i whakauruhia, i haere tonu ia ki te purei i te OHL mo te waa 2013-14 a i eke ki te 157th katoa i waenga i nga kaitakaro o Amerika ki te Raki na te NHL Central Scouting Bureau. I te mutunga ka tohua a Joshua i te rauna tuarima, 128 o te katoa, i te
2014 NHL Entry Draft na te Toronto Maple Leafs. Kāore ia i mōhio i whakauruhia ia kia tae ra ano ki te wā i waea mai ai te kaiwhakahaere o Toronto ki a ia i a ia e noho ana i roto i te motokā. Whai muri i te tuhi a Joshua, i korero nui a Leafs kaiwhakahaere kaitirotiro amateur a Dave Morrison mo ia hei kaitakaro, e kii ana: "He teitei ia, he tino hakinakina, ana i kite maatau i etahi rama o te tino pukenga pai i te mutunga o te tau. Kāore e taea e ōna kaiako te kī i ngā mea pai mō ia. He tino pukumahi ia i ngā huarahi e rua o te kēmu, he kaitākaro nui rawa atu". I noho a Joshua i nga tau e rua ki te Stampede, i te wa i awhina ai ia ki a raatau ki te wikitoria i te whakataetae Clark Cup 2015.