5. Wesley Matthews
The Mavs created cap space in the 2015 offseason in hopes of significantly improving their roster around an aging Dirk Nowitzki. They got a verbal agreement from DeAndre Jordan before he changed his mind and returned to the Clippers. Dallas had a deal in place with Matthews, and when DJ stayed in LA, the Mavericks gave the 6’4 wing more money. They worked out a four-year $57 million contract that was increased to $70 million.
Matthews was a key role player for the Blazers but was coming off a torn Achilles and Portland never advanced beyond the second round of the playoffs. There was zero guarantee that the 6’4 guard would be the same player, and he would have to improve to live up to his massive contract.
The deal quickly became a sunk cost. Matthews was a steady role player, but his poor shot selection and head-scratching passes were problematic. The Mavericks made the playoffs in his first season but were bounced by the Thunder in the opening round. They won just 57 games over the next two years combined and were in full rebuild mode.
It had been time to trade Wesley Matthews before they finally did in 2019. He was sent to New York in the Kristaps Porzingis deal and is currently on his fifth team since leaving Dallas. Matthews never lived up to his contract, and the Mavs should have quickly moved on during their rebuild.