4. Justin Jackson
Justin Jackson started in 14 games over two seasons for the Mavericks just a few years ago, and now he's back with the Texas Legends (the Mavericks' G League affiliate) after bounding around the NBA since leaving Dallas.
In 14 starts for Dallas, Jackson averaged 11.1 points, 3.2 rebounds, and 1.6 assists per game while shooting 34.6 percent from downtown. Dallas was 7-7 in games that he started but were 1-4 in games that he started and played 30 minutes or more.
People had high hopes for Jackson, as he showed some early flashes, but he was not great during his time in Dallas. Jackson didn't defend well, didn't shoot well, and regressed after one season in Dallas. His game took a steep decline, and he didn't show much promise as a young prospect.
Dallas decided to trade him to the Thunder with one year left on his contract and has had a rough stretch over the last few years or two. He has found himself back in the G League after being a top-15 pick back in 2017.
Jackson could revive his career with a great stint with the Legends this season, but it seems unlikely that he ever ends back on the Mavs. Everything that the Mavericks like in wings, he doesn't do well.