Kammala jumla mai zuwa: Mantzaris ya zama memba na manyan 'yan wasan kwallon kwando na Girka a shekara ta 2011. Ya kasance memba na manyan kungiyoyin kwallon kafa na Girka da suka buga a 2012 FIBA World Olympic Qualifying Tournament, da 2014 FIBA World Cup, da kuma EuroBasket 2015. Ya kuma taka leda a
2016 Turin FIBA Gasar Wasannin Wasannin Olympics ta Duniya, da kuma a EuroBasket 2017.