1988–89 Dallas Mavericks season

The 1988–89 Dallas Mavericks season was the ninth season for the Dallas Mavericks in the National Basketball Association. During the off-season, the team signed free agent Terry Tyler. After reaching the Conference Finals last year, the Mavericks got off to a fast start by winning nine of their first twelve games of the regular season. However, after a 17–9 start to the season, the team posted a seven-game losing streak in January, and later on held a 24–21 record at the All-Star break. In January, sixth man Roy Tarpley was suspended indefinitely for violating the league's anti-drug policy; Tarpley was also out with a knee injury, only playing just 19 games.

At mid-season, the team traded All-Star forward Mark Aguirre, who had several incidents with the team during the season, to the Detroit Pistons in exchange for former All-Star forward Adrian Dantley, and dealt Detlef Schrempf to the Indiana Pacers in exchange for Herb Williams. Aguirre would win a championship with the Pistons, as they defeated the 2-time defending NBA champion Los Angeles Lakers in a four-game sweep in the 1989 NBA Finals.

After hovering a few games over .500 in winning percentage for most of the regular season, the Mavericks collapsed and suffered a 12-game losing streak in March, which sealed their fate for the entire season. The Mavericks finished in fourth place in the Midwest Division with a 38–44 record; it was the first time since the 1982–83 season that the team failed to qualify for the NBA playoffs, as they finished just one game behind the 8th–seeded Portland Trail Blazers.

Dantley averaged 20.3 points per game in 31 games after the trade, while Rolando Blackman averaged 19.7 points and 3.7 assists per game, and Derek Harper provided the team with 17.3 points, 7.0 assists and 2.1 steals per game, and also led them with 99 three-point field goals. In addition, Sam Perkins provided with 15.0 points and 8.8 rebounds per game, while Tarpley contributed 17.3 points, 11.5 rebounds and 1.6 blocks per game, and James Donaldson averaged 9.1 points, 10.8 rebounds and 1.5 blocks per game, but only played 53 games due to a knee injury. Meanwhile, Williams averaged 6.6 points, 6.6 rebounds and 1.8 blocks per game in 30 games, Brad Davis contributed 6.4 points and 3.1 assists per game, Tyler provided with 5.5 points and 3.0 rebounds per game, and Bill Wennington averaged 4.6 points and 4.4 rebounds per game.

During the NBA All-Star weekend at the Houston Astrodome in Houston, Texas, Harper participated in the NBA Three-Point Shootout. The Mavericks finished eighth in the NBA in home-game attendance, with an attendance of 695,056 at the Reunion Arena during the regular season. Following the season, Tyler was released to free agency.