Mitchell muttered, "If that's what he needs to win f---ing MVP, f--- it," while walking into Utah's locker room after Sunday's Game 4 loss put Utah on the brink of elimination.
Video of the moment, posted by a Salt Lake City television reporter, went viral.
Mitchell expressed regret after Tuesday's shootaround that the comment was caught on tape, attributing it to frustration.
"Obviously he's the MVP. There's no doubt about that," Mitchell said. "I'm pretty sure we've all said things in the heat of the moment when you get upset. It was more so just about myself. You try so hard to fight back and what we did. I'm definitely upset that it came out that way, but you can't do anything about it. I understand that there are cameras everywhere. I'm getting used to that. But like I said, he is the MVP, rightfully so."
Mitchell acknowledged that the comment was a reference to what he perceived as Harden, who is expected to win the first MVP of his career after two runner-up finishes, receiving favorable foul calls. However, that wasn't a major factor in Game 4, when Harden attempted eight free throws, fewer than his season average and only one more than Mitchell attempted that night.
"I'm really focused on just going out here and seeing what we can do for Game 5 and not really complaining about the calls," Mitchell said. "That's not who I am."