Rantanen ya ci gaba da ci gaba a cikin tawagar matasa na Finnish a cikin zabin da ya samu a gasar zakarun duniya na matasa na 2015
a birnin Toronto. Duk da rashin nasarar da aka samu a matsayi na bakwai, Rantanen ya ba da gudummawa tare da kwallaye hudu a wasanni biyar don samun dan wasa na uku a cikin zabin tawagar.