When James Harden picked up his sixth foul trying to stop Shawn Marion with 4:49 left to go in the Oklahoma City Thunder's stunning Game 4 loss to the Dallas Mavericks, few thought much of it. The Thunder were already up 15 points and probably had the game in the bag. In the end, we know that the Mavericks completed a stunning rally to win in overtime. As it turned out, it began right when Harden fouled out.
From that point on, the Mavericks outscored the Thunder 28-6, grinding Oklahoma City's offense to a halt. The Thunder shot just 3-16 from the field after Harden left the game, and threw in four turnovers for good measure. Harden's absence forced the Thunder to go with Thabo Sefolosha, a complete non-factor on offense. That allowed Dallas to lock in more on Kevin Durant and Russell Westbrook without having to worry that the other three players would beat them. It's no accident that Durant went 0-6 (including 0-5 from three-point range) and committed three turnovers during that span. He couldn't get the ball in scoring position, and without Harden, the Thunder didn't have a secondary playmaker.
We've talked before about the importance of Harden as a bridge between the somewhat divergent talents of Westbrook and Durant. Harden's playmaking ability mitigates Westbrook's sometimes-shaky decision making, and his scoring ability, especially with his ability to spot-up and hit three-pointers, gives Durant more space to operate. Without him on the floor, the Thunder have too few scoring options, and it kills them in tight possessions when they need a basket. That's precisely what caused the Game 4 collapse, and it could have been avoided if Harden was more judicious with his fouls.