James Harden is once against having an MVP level campaign where he is proving that he is one the greatest offensive players this league has ever seen. He has mastered things on offense in ways that no one else in the league has, and he is probably the most frustrating offensive player to have to defend in the NBA.
When you are thinking about how you want to contain the most frustrating offensive weapon in the NBA, one of the first places you could look is the most frustrating defensive player in the NBA, and that is what makes his matchup with Marcus Smart so fascinating.