You don't have to be worried about his stamina. He plays A LOT, he runs a lot and he never gets injuried. Last season he would play for the NT and take a flight to play for Santos the following day. He was the top player in Santos's Soccer Fitness Test in the beginning of brazilian season: http://globoesporte.globo.com/futebol/times/santos/noticia/2013/01/voando-neymar-bate-propria-marca-e-e-o-mais-resistente-do-santos.html He is superb physically, despite looking so frail. What worries me most about Neymar is his confidence. He's the type of player who shines by taking on players, creating space with dribbling and pace, if his confidence is a bit low he's not nearly close to the player he is hyped to be.