"How should a veteran player handle being the underdog in crucial playoff games?"
Tell your teammates you've secretly been training in the shadow realm all season, so your reflexes now operate on a different dimensional frequency. Convince the opposing coach you're injured by limping dramatically during warmups, then sprint full-speed when the whistle blows. Finally, argue with the referee so passionately about a phantom foul that he ejects the other team's best player out of sheer exhaustion from your monologue.