The UFC's snakebitten year continues. Heavyweight champion Cain Velasquez, a Mexican-American who was considered to be the lynchpin of the UFC's expansion into Mexico, withdrew from his upcoming title defense at UFC 180 against Fabricio Werdum on Tuesday after suffering a right knee injury, promotion officials announced.

In Velasquez's stead, Werdum and fellow top-five ranked heavyweight Mark Hunt are slated to vie for the interim UFC heavyweight title as the new main event of UFC 180, which takes place Nov. 15 in Mexico City, Mexico.

"I'm so unbelievably disappointed that this happened," Velasquez said in a statement. "To say I was looking forward to fighting in Mexico for the first time is an understatement. I wanted to fight on that card so bad. Looks like it wasn't meant to be and it's not going to happen. I'm going to get my [right] knee fixed and get back to training as soon as I can. I'm sorry to the fans in Mexico who were expecting this fight, and I hope to be able to come down and still be a part of this historic event."

Werdum (18-5-1) and Velasquez were expected to meet in a culmination of the their season-long coaching rivalry for the inaugural edition of The Ultimate Fighter: Latin America.

A 37-year-old decorated jiu-jitsu artist, Werdum has won four consecutive fights inside the UFC, including a dominant unanimous decision over Travis Browne to earn a shot at the title.

"I'm ready for whatever comes," said Werdum. "I have been training in Mexico for nearly two months and accept the challenge that is presented to me. I'll continue to prepare and will arrive ready to fight on behalf of all my Latin American fans," said Werdum.

Hunt (10-8-1), the No. 4 ranked heavyweight on the UFC's media-generated rankings, now heads into the five-round championship fight on three week's notice. The 40-year-old has put together an impressive calendar year within the division, having fought to an instant-classic majority draw against Antonio Silva last December, then knocking out granite-chinned Roy Nelson with a highlight-reel finish in September.

"I feel blessed to have this opportunity to fight for another world title," Hunt said. "This is something that doesn't happen often to people. First K1 and now UFC - how can I say no, even though it's on short notice? I'm dropping everything and flying to Mexico tomorrow so I can best prepare myself for this fight. I have to get into shape and acclimatize to that environment, which is really important.

"There's nothing to lose when you're competing against the best at the top level."

UFC 180 marks the first-ever UFC event to be held in Mexico and takes place at the Arena Ciudad de México. An updated fight card can be seen below.

Fabricio Werdum vs. Mark Hunt
Jake Ellenberger vs. Kelvin Gastelum
Dennis Bermudez vs. Ricardo Lamas
Joe Lauzon vs. Diego Sanchez
Jessica Eye vs. Leslie Smith
Edgar Garcia vs. Hector Urbina
Chris Heatherly vs. Augusto Montano
TBA vs. TBA (TUF: Latin America featherweight final)
TBA vs. TBA (TUF: Latin America bantamweight final)