Thomas has informed the team that his wife's illness, which took him away from the club last season, will prevent him from playing a 14th NBA season, Thomas' agent Bob Myers said Tuesday.
The 6-foot-10 power forward had agreed to a one-year deal with Dallas last month. Last season, he averaged 7.5 points and 2.3 rebounds in 18 games. Thomas left the Mavs on good terms in January to care for his wife. He has not disclosed the nature of her illness.
Mavs officials declined to comment as they work with the league to void his contract. He had signed for the veteran's minimum of $1.35 million.
The Mavs are left with one true power forward on the roster, Dirk Nowitzki, and 13 guaranteed contracts.
Jeff Caplan covers the Mavericks for ESPNDallas.com. You can follow him on Twitter or leave a question for his mailbag.