A perceived lack of respect from officiating crews toward Dirk Nowitzki has pushed Avery Johnson to the boiling point.

The coach has been confounded by the fact that Nowitzki is going to the free-throw line nearly two fewer times per game this season after averaging 9.1 trips last season.

Asked if Nowitzki is granted the appropriate respect by referees, Johnson said:

"Not like a superstar. If you look at all of the superstar guys who haven't won a championship, to me, he doesn't get the respect that he should.

"I don't know if he needs to wag his tongue more. I don't know if he needs to change his appearance. I don't know what he needs to do."

Johnson said superstars such as Kobe Bryant, Shaquille O'Neal and Tim Duncan, who have won multiple championships, can be excluded from Nowitzki's class. But others, such as Allen Iverson, LeBron James and Tracy McGrady, seem to get the benefit of the doubt from refs more than Nowitzki, Johnson said.

Indeed, Nowitzki is tied for 19th in trips to the line per game at 7.3.

"To me, he's one of the top players in our game," Johnson said. "That's a pretty select class of people.So, if he's a top five player in the world, and he's a professional and he works hard and he's not a quitter ... I don't know what we have to do to get him catapulted and change the perception of who he is. He is a legitimate superstar.

"It's just that we're living in a world where it's style over substance."