He played college basketball for Western Carolina University, where in his junior year, he averaged 24.9 points per game, which ranked second in the nation.

[1] He played for Zanesville High School and was fourth in the voting for Ohio Mr. Basketball as a Senior, finishing behind the first Sophomore winner LeBron James.

This included a start at small forward due to Ron Artest being suspended for Game Two of the team's first-round playoff series against the San Antonio Spurs following a flagrant foul (elbow to the head) on Manu Ginóbili.

[7] When interviewed on a segment by TNT during a game, Martin credited Doug Christie for helping him learn how to defend in the NBA.

In the general managers' survey at the start of the 2006–07 NBA season, Martin tied for second as the player most likely to have a breakout campaign, behind the Orlando Magic's Dwight Howard.

[9] On March 17, 2007, Martin led the Kings to a 95–83 road win over the Orlando Magic and joined Nate Archibald as the only other player in NBA history to score at least 20 points in a game with only one field goal made.

Martin finished the season 6th in the NBA in scoring at 23.7 PPG, 4.5 RPG, 2.1 APG and averaging 45% from the court and 40% from three-point range.

[13] On November 2, 2009, Martin scored 48 points including 7–10 from three-point range to lead the Kings to an overtime victory over the Memphis Grizzlies.

[15] In his debut as a Rocket, Martin scored just 3–16 from the field, but 8–9 from the line, ending the game with 14 points, in a 125–115 loss to the Indiana Pacers.

After commissioner David Stern, acting as owner of the New Orleans Hornets at the time, vetoed a three-team deal involving the Rockets and the Los Angeles Lakers that would have sent Martin, Luis Scola, Goran Dragić, and Lamar Odom to New Orleans, he stayed with Houston for the lockout-shortened season.

[20] With new rules regarding foul calls, in addition to playing injured, Martin's numbers dropped, averaging just 17.1 points per game, the worst in his career as a full-time starter.

[21] On October 27, 2012, Martin was traded along with Jeremy Lamb and three future draft picks to the Oklahoma City Thunder for James Harden, Daequan Cook, Lazar Hayward, and Cole Aldrich.

[22] In game six of the Western Conference Quarterfinals, Martin scored 25 points in a 103–94 win, as the Thunder eliminated his former team the Houston Rockets.

On July 11, 2013, he was officially acquired by the Timberwolves as part of a three-team trade involving the Thunder and the Bucks that sent the rights to Szymon Szewczyk to Oklahoma City and Luke Ridnour to Milwaukee.

[30] Martin's final appearance came on May 12, 2016, in the Spurs' loss to the Oklahoma City Thunder in Game 6 of the Western Conference semi-finals; he recorded two rebounds in just under six minutes off the bench.

"[35] On October 1, 2019, the Brisbane Bullets of the National Basketball League (NBL) announced their new ownership group, which included Martin.