During the 2003–04 season, Lang was enjoying another career year and recorded his first career hat-trick on November 12, 2003. He was leading the NHL in scoring when he was traded to the Stanley Cup-contending Detroit Red Wings for prospect Tomáš Fleischmann, a first-round draft pick (Mike Green) in 2004 and a fourth-round pick in 2006. This marked the first time in NHL history that a player was traded while leading the NHL in points. Shortly after the trade, he was sidelined with a broken rib on March 8. Missing 13 games, he surrendered the NHL scoring lead to the Tampa Bay Lightning's Martin St. Louis and finished with 79 points in 69 games, one point shy of his career-high set in 2000–01 and ninth overall in the League. (Lang's points-per-game of 1.14 was identical to St. Louis'.) Lang returned to the Red Wings in time for the 2004 playoffs, but the team was eliminated by the Calgary Flames in the second round. He recorded a career-high nine points in 12 playoff games.