Mark Cuban insists he is unconcerned. Of course, even if he were anxious about Dirk Nowitzki’s sore left knee, he probably wouldn’t let on. No sense in agitating the paying customers with such news. “But you’d be able to tell I was concerned,” he said. Cuban explained before Friday’s game against the Heat that Nowitzki’s body at age 35 simply isn’t the same as it was 10 years ago. The physical problems are more noticeable, the owner said. And when Nowitzki makes an equipment change like wearing a protective sleeve on his knee, it raises questions. “That happens to every player,” Cuban said. “You get to be 35, and you have aches and pains. So I don’t think there’s a problem there. The sleeve I think was just for precaution more than anything because he was sore. Dirk’s been aware of every ache and pain since he’s been 21. So it’s not something I was concerned about.” Nowitzki came out firing against the Heat with three quick 3-pointers in the first six minutes. When his 3-point shot is pure like that, it generally means his knees are not bothering him much.