LeBron James famously debuted for the Cleveland Cavaliers during the 2003-04 season, and he did so as the team's shooting guard. James played in 79 of 82 games in his age-19 season, mainly at guard, and fantasy basketball managers certainly enjoyed the numbers.
James averaged 20.9 PPG, 5.5 RPG and 5.9 APG, but there was always a sense that things would get considerably better in Year 2. They sure did, and for every season after that and still going, perhaps partly because the Cavaliers quickly realized James was better suited to play small forward.