Alvarez was drafted first overall by Shell Turbo Chargers in the 2004 PBA Draft, ahead of former college rival James Yap. He played his first PBA game on the team's second game after former coach John Moran benched him in the first game. He thought that Alvarez was not yet ready to play, but when Leo Austria took over the team's coaching duties, his game status went up and won the Rookie of the Year honors at season's end. In his rookie season, he averaged 8.8 points and 6.4 rebounds in 72 games.