But it was only in the next season that the Mavericks finally broke through. They started the 2002–03 season with a 14–0 record, which was one win shy of tying the NBA record set by the 1993–94 Houston Rockets (15–0). The Mavericks finished with a 60–22 record in the regular season, astonishing fans and critics with their sparkling offense. Since acquiring the "Big Three" of Nowitzki, Finley, and Nash, the Mavericks were a Western Conference power in waiting and finally led the team to the Conference Finals against the San Antonio Spurs. However, with the series tied 1–1, Dirk Nowitzki, the team's leading scorer, suffered a knee injury in game three that kept him out the rest of the series. This further worsened the Mavs' front-court depth problems (both of their backup centers were injured for the entire series) and the Spurs took the series in 6 games.

In 2003–04, two blockbuster trades were announced. The Mavericks acquired Antawn Jamison, Danny Fortson, Jiří Welsch and Chris Mills from Golden State in exchange for Nick Van Exel, Evan Eschmeyer, Popeye Jones, Avery Johnson and Antoine Rigaudeau. Another high-profile trade sent Raef LaFrentz, Chris Mills and Jiří Welsch to Boston for Antoine Walker and Tony Delk. Although the team struggled with chemistry, the Mavericks easily qualified for the playoffs. With the trio Nowitzki-Finley-Nash and NBA Sixth Man of the Year Jamison, the Mavericks continued their reputation as the best offensive team in the NBA. Notable were two rookies, Josh Howard and Marquis Daniels, who made an immediate impact. However, the Mavericks were eliminated quickly in the playoffs, losing in the first round to the Chris Webber-led Sacramento Kings, a team which clearly played better defense. The Mavericks management had to re-evaluate their strategy.