DALLAS (AP) – Dirk Nowitzki’s 20th season is over a few games early after the Dallas Mavericks star had surgery on his left ankle. The team said Nowitzki had a procedure to clear out unhealthy tissue and promote healing, called surgical debridement. It was performed at a Dallas medical clinic. The 39-year-old Nowitzki played his final game of the season at home against Portland on Tuesday. He has said he plans to return for a 21st season, all with the Mavericks.