 Nyorai mberi kweiyi ndima - Mushure mekushamisika nechikwata chepakati cheIreland, Masterson akashevedzwa kuchikwata cheIreland chepasi pemakore gumi nemasere kutanga kwegore ra2010. Akava kaputeni wechikwata chacho gore rakatevera racho. Pasinei nerekodhi yake nechikwata chepasi pe-18, kukuvara kwakadzivisa Masterson pakazosvika nguva yekukwira kuchikwata cheIrish chepasi pe-20. Masterson akaita chitarisiko chimwe mu2013 Six Nations Under 20s Championship, achitamba neScotland. Pashure pokusiyiwa kunze kwechikwata cheIreland nokuda kwe2013 Junior World Cupakachinja kuvimbika kuScotland, kwaakakwanisa kutamba nokuda kwababa vake, uye akawedzerwa kuchikwata chavo. Akaratidza mumitambo yese mishanu yeScotland pamutambo, achitanga mune maviri acho, uye achiedza kubva pabhenji kurwisa Wales, sezvo Scotland yakapedza 10th yakazara. 