15. Darren Collison
The Mavs traded Ian Mahinmi to Indiana in 2012 for Collison and Dahntay Jones. It was a bit of a surprising move, but Dallas had a hole at point guard after Jason Kidd departed for New York. The 25-year-old Collison helped the Pacers reach the playoffs two straight years and most expected him to be the starter for the Mavericks.
He only opened 47 games as the position was in flux most of the season. Head coach Rick Carlisle preferred a veteran, and the Mavericks even signed Derek Fisher off his couch to start nine games before that experiment blew up. Collison put up strong numbers, including averaging 12.0 points, 5.1 assists, and 1.2 steals in 29.3 minutes per game, but he never nailed down the position.
Injuries limited superstar Dirk Nowitzki to just 53 games, and the Dallas Mavericks missed the playoffs in 2013 for the only time in 16 years.
Darren Collison departed in free agency after just one year. He signed with the LA Clippers to back up Chris Paul where he rebuilt his reputation. In 2014, Collison joined the Kings where he had arguably the three best years of his career.
The six-foot point guard was undersized, but he was a valuable contributor that did not mesh with head coach Rick Carlisle. That forced him to leave the Dallas Mavericks far too soon.