He can call it what he wants, but the bottom line is that he didn't have the energy/power to maintain the pace that he had in round one.
He got fatigued. Period.
I hope he stops trying to make excuses.
This is all part of the game. Pacing yourself, nerves, cardiovascular efficiency, etc, are all the same really.
If you fail to control any one of these aspects, you can fatigue.