The Cavaliers already featured Zydrunas Ilgauskas as the team's starting center, so coach Mike Brown moved Wallace to the power forward position. Wallace played in 22 regular season games (all starts) and averaged 4.2 points, 7.4 rebounds and 1.7 blocks per game. Wallace had a Cavalier regular season high of 12 points on February 24, 2008, against the Memphis Grizzlies, and had regular season Cavaliers' highs of 15 rebounds against the Charlotte Bobcats and four blocks against the Orlando Magic. In the playoffs, Wallace played in 13 games (all starts) and averaged 3.2 points, 6.5 rebounds and 1.1 blocks per game. He had his playoff high of 12 rebounds in Game 4 win against the Washington Wizards in the first round of the playoffs as the Cavaliers swept the Wizards. The following series would be against the resurgent Boston Celtics. The series would go to seven games, with the Celtics winning the final game at home and Wallace failing to register double figure rebounds in the series.
Even in limited minutes, Wallace had a significant impact on the Cavaliers' defense. Prior to Wallace's first game with the Cavaliers against the Memphis Grizzlies, Cleveland had allowed 98.2 points per game through 55 games. After acquiring Wallace, Cleveland's defense finished the season allowing 96.7 points per game, the ninth best mark in the league. In the 2008 playoffs, the Cavaliers' defense greatly improved, holding opponents to 87.8 points per game and posting a Defensive Rating of 102.1. The Cavaliers ranked first among all 16 teams in both defensive categories for the playoffs, ahead of even the Celtics led by Kevin Garnett, the Defensive Player of the Year.