Harden struggled from the outset, missing his first eight shots from the field and getting six shots blocked on the night. He wound up shooting 3 for 16 and finished with 17 points, three assists and three turnovers.
“I just think James was probably pressing a little a bit,” said Sampson, who has served as Houston's interim coach since McHale left to be with his family on Nov. 10. “I'm not sure he would admit it.”
Cook started in place of injured forward Chandler Parsons (shoulder) and finished with 18 points, seven rebounds, four assists, one steal, one block and three turnovers.
In addition to physical and emotional fatigue, the Rockets' biggest shortcoming might have been the loss of Parsons, who has played well in the past defending Kevin Durant.
As a whole, Houston (7-8) has always played the Thunder tough and still leads the all-time series 9-7, but there wasn't enough juice left in the tank Wednesday.
Sampson mentioned one more determining factor.
“This is a good team, man,” Sampson said of the Thunder (12-4). “They've got weapons. Kevin Martin is a great fit for this team because Durant and (Russell) Westbrook can get in the paint.
“They're good. They have a perfect symmetry here. They have fans, a great team and that makes it a tough place to play. Yeah, we've had a tough 24 hours, but give OKC some credit.”