Seattle SuperSonics / Oklahoma City Thunder (2003–2018) Draft year injury and relocation (2003–2008) Collison was selected by the
Seattle SuperSonics with the 12th overall pick in the
2003 NBA draft but missed the
2003–04 season with injuries to both shoulders. He made his NBA debut on November 3, 2004, recording two points, five rebounds, and two assists in a 114–84 loss to the
Los Angeles Clippers. Collison appeared in all 82 games in the 2004–05 season, averaging 5.6 points, 4.6 rebounds, and 0.4 assists in 17 minutes per game. He played in all 82 games for a second time during the 2006–07 season, averaging 9.6 points, 8.1 rebounds, and 1.0 assist in 29 minutes per game. On January 9, 2007, Collison had a career-best game with 29 points and 21 rebounds in a 113–102 loss to the
Phoenix Suns. In 2008, the franchise relocated to Oklahoma City and rebranded as the Thunder.
Finals appearance and later years (2008–2018) On December 19, 2010, Collison scored a season-high 19 points and added eight rebounds in a 120–113 loss to the
Phoenix Suns. In the game, he also drew his 15th charge of the season, a majority of the 22 charges the Thunder had drawn as a team to that point in the season. That postseason, on May 15, 2011, Collison helped the Thunder to a Western Conference Semifinals Game 7 105–90 victory over the
Memphis Grizzlies, with eight points and a playoff career-high 12 rebounds. In the Western Conference Finals, Collison and the Thunder lost to the
Dallas Mavericks in five games. In 2012, Collison helped the Thunder make the leap to the next level and reach the
NBA Finals, where they lost in five games to the
Miami Heat, who were led by Collison's fellow 2003 draftees
LeBron James,
Dwyane Wade, and
Chris Bosh. On February 3, 2015, Collison signed a two-year, $7.5 million contract extension with the Thunder. On July 21, 2017, Collison re-signed with the Thunder to a one-year, minimum salary deal. His final NBA game was played on April 11, 2018, a 137–123 victory over the
Memphis Grizzlies, where Collison recorded a point and a rebound.
Retirement On May 10, 2018, Collison announced his retirement from professional basketball. On January 12, 2019, the Thunder announced that Collison's 4 jersey would be retired on March 20, becoming the first number retired by the Thunder. ==Post-playing career==