Dirk Nowitzki and the Dallas Mavericks lost The Finals in 2006 to the Miami Heat, but defeated them in a relative upset in 2011.

"I think we were fortunate to see them in Year 1 of them getting together," said Nowitzki. "They took their games to another level, figuring out even better how to play off each other, play with each other. They looked almost unbeatable for a while."

The Heat went on to win The Finals in 2012 and 2013 while the Mavericks took a big step backwards.

"Dirk was the best player in the world—at that time, during that series," Riley said.