Roy Nelson's performance against Frank Mir was nothing short of terrible. He looked out of breath throughout the second and third rounds, and was unable to generate offense for much of the bout. According to his wife, Nelson's problems were from a bout with pneumonia, not a lack of conditioning.
Via text messages with Cagewriter, Jessy Nelson said that her husband had walking pneumonia during the first two weeks of May, and that he spent Monday in a Las Vegas hospital. "He described the feeling like someone is taking a big scab off of his lungs," Nelson wrote.
That would certainly explain the wheezing that went on during the Mir match. It would be easy to blame his conditioning on his appearance, as Nelson flaunts his beer-bellied figure. He even walks out the Octagon to the "Weird" Al Yankovic song, "I'm Fat." UFC president Dana White said that he was unhappy with Nelson's performance and planned to meet with him about it.
But Nelson was just as full-figured in his bout with Junior dos Santos, which also went all three rounds. Though he tired near the end of that bout, it was nothing like the exhaustion Nelson showed in the Mir bout.
His other two bouts in the UFC were both first-round knockouts. Before that, his last three-round bout was a loss to Jeff Monson in March of 2009. His last decision win was nearly four years ago.