DALLAS — Dallas Mavericks 11-time All-Star forward Dirk Nowitzki underwent arthroscopic surgery to his right knee Friday morning.The Mavericks said the surgery was successful and that the 15-year veteran will be sidelined for about six weeks.Mavericks team physician Dr. T.O. Souryal performed the surgery at Texas Sports Medicine. Nowitzki has missed the past three preseason games with swelling and soreness in his right knee. His place in the starting lineup will be taken by Elton Brand, whom the Mavericks acquired in the off-season after he was released by the Philadelphia 76ers via the NBA's amnesty clause.Earlier this week when Nowitzki was tinkering with the idea of surgery, center Brandan Wright said, Weve just got to play basketball. I know hes got a lot of uncertainty with his knee and stuff like that. We dont really know whats going to happen with it. If it goes well or if it doesnt, weve just got to be prepared to play without him.Now, that preparation has arrived, since Nowitzki may not return until the middle of November.Six weeks from Friday is Nov. 30. If Nowitzki were to return for the Mavericks' home game against Detroit on Dec. 1, he would have missed 16 games, including two games against the Los Angeles Lakers. Dallas opens at the Lakers on Oct. 30 and plays at home against the Lakers on Nov. 24. After opening the season with back-to-back road games against the Lakers and the Utah Jazz, the Mavericks' next three games are at home against three non-playoff teams from last season: Charlotte, Portland and Toronto.The Mavericks play their fifth exhibition game of the season at Atlanta on Saturday. Nowitzki hasn't played since the preseason opener, Oct. 6 in Berlin.