Howard, who played for Dallas during parts of the 2000-01 and '01-02 seasons, can't sign with the Mavericks until he clears waivers tomorrow, the same day Dallas plays its season opener at Cleveland.

"Juwan was too big of an opportunity to pass up," Donnie Nelson, president of basketball operations, said in a story on the team's Web site. "Juwan is a winner, he's a leader and he knows the Maverick way."

Howard is expected to play immediately. He and the Minnesota Timberwolves agreed to a buyout yesterday, and the Cavaliers were among the teams interesting in signing him.

Center Erick Dampier and swingman Devean George won't play in the Mavericks' season opener because of injuries.

To make room for Howard, the Mavericks waived center DJ Mbenga.

Mbenga averaged 1.3 points and 0.9 rebounds in 79 games the past three seasons for the Mavericks. The 7-footer played only 21 games last season before tearing ligaments in his right knee Feb. 7. He played in only one preseason game, and had five rebounds and two blocked shots in 12 minutes.

"DJ needs an opportunity to play and develop," Nelson said. "We're hopeful that with playing time, whether it's in the NBA or Europe, he'll be able to join our team in the future."

Also Tuesday, the Mavs exercised their 2008-09 contract option on second-year guard Maurice Ager, their first-round pick in 2006. Only the first two years of a first-round draft pick's contract are guaranteed, while the third and fourth years are team options.