An injury to Dan Henderson has forced an unprecedented cancellation of a major UFC event.

UFC president Dana White announced on Thursday that because Henderson, who was set to challenge Jon Jones for the UFC light heavyweight championship at UFC 151 on Sept. 1 in Las Vegas, suffered a partially torn MCL, the event would be canceled.

Jones will instead fight former champion Lyoto Machida on Sept. 22 in Toronto.

"This is one of my all-time lows as a president," said White. "For the first time, in 11 years we're gonna cancel an event."

During the teleconference, White said that when he found out about Henderson's injury, former middleweight contender Chael Sonnen was offered the bout with Jones and accepted, but Jones refused to accept the fight. White also said that Machida was offered to take the spot on Sept. 1, but was in flight to Brazil and the couldn't make the circumstances work. "I can accept why Machida didn't take the fight," White said.

With a weak undercard and no other viable main-event alternatives worth asking customers to spend $50 on, White pulled the plug on the event.

The UFC president clearly placed the blame for the fight cancellation on the champion.

"Chael Sonnen accepted the fight with Jon Jones last night," White said. "At 8 or 9 last night the one thing I never thought would happen in a million years happen. Jon Jones said, I won't fight Chael Sonnen on eight days notice. That has never happened either."

White said that the company has not yet figured out what will happen to the remainder of the fights scheduled for the card. Fans who purchased tickets for the event will be able to get refunds at the point of purchase.

While a planned March event in Montreal was canceled, this marks the first time a UFC event will be canceled with a full card announced. White acknowledged the company doesn't know how much of a hit it will take for the cancellation.

"It’s major, major deal," said White. "We lose [expletive] of money, money that’s already been spent. We’re eight days out. We’ve spent [expletive] of money on this fight. How long, how far it goes and how bad it hurts. I don’t know because it’s the first time we’ve done it."

White held steadfast in his belief that the UFC is not running too many events, despite a summer filled with fights canceled due to injuries and now a major event cancelation.

"We’ve built this industry, we know what we’re doing," he said. "There are going to be things coming up, like injuries, and guys who don’t want to fight anybody. It has nothing to do with business. .. nothing to do with too many cards and cards stretched too thin."

White's anger level didn't subside as the teleconference went on, if anything, he got angrier. The majority of his wrath was vented at Jones' coach, Greg Jackson, whom White said counseled Jones not to take the bout.

"The guys a [expletive] sport killer," said White. Later, he added. "Greg Jackson should never be interviewed by anyone again, except a psychiatrist."

Moments after the press conference ended, reaction started pouring in from around the MMA world. Henderson posted the following statement to his Facebook page:

"Sadly and unfortunately, I partially tore a ligament in my knee in training," the post read. "As a result I've had to make one of the toughest decisions that I have ever had to make...for the first time in my career I am forced to pull out of a fight, my fight with Jon Jones at UFC 151. Luckily, surgery is not needed at this time and I will be completely devoted to rehabbing my knee as quickly as possible. I feel that I owe it to my fans and all the people supporting me to fight at my full potential in order to give myself a chance to win the UFC title. I appreciate the loyal support that I have felt from my fans. I want to thank all of my coaches and team of guys for the great support with my training camp. Most importantly, I appreciate their honesty when I needed them the most to make this very difficult decision. I also want to thank Dana and Lorenzo for being so understanding and supportive. I will continue to pursue the UFC belt with all of my heart!"

Jackson told Mauro Ranallo on The MMA Show, "I was asked if it was smart to take a fight on three days notice and I don't think it's smart to do that. Three days to fight a guy that caliber is not a smart thing to do. I'm not trying to ruin the sport or cancel an event. I don't know about that stuff, but thought it wasn't a wise course of action."