The Dutch fighter was injured in his training camp according to an initial report by MMAFighting.com. Additional sources confirmed the news independently to Bleacher Report on Wednesday.
The nature of the injury that forced Overeem out the fight was a torn quadriceps muscle in his leg that will push him out of training and out of UFC 160.
Alistair Overeem @Alistairovereem
Injured! Caught a slightly tear in my quad muscle so unfortunatly out of may 25's UFC. Not happy to let you guys 'the fans' down!2013-3-7 14:38:08
The injury knocks out one of the prime heavyweight fights of the next few months, especially considering the heated rivalry between Overeem and dos Santos over the last year. This is the second time their fight has been delayed.
Dos Santos and Overeem were originally scheduled to fight at UFC 146 in 2012, but Overeem tested positive for elevated levels of testosterone during a pre-fight drug screening. He was forced out of the bout and was suspended for nine months.
Prior to his fight against Cain Velasquez at UFC 155, when dos Santos was asked about facing Overeem in the future, he took a jab at the former K-1 champion following his 2012 suspension for having elevated levels of testosterone.
“I prefer to fight against those athletes, clean athletes, and real professionals," Dos Santos said.
“Guys like me and Cain Velasquez, we are made in the gym. Guys like the other guy (Alistair Overeem) they are made at the laboratory.”
Overeem took the fight with dos Santos after suffering a loss in his last fight to Antonio "Bigfoot" Silva at UFC 156. It was his first defeat at heavyweight since a 2007 loss to Sergei Kharitonov in Japan.
While the injury to Overeem's leg will cancel his fight against Dos Santos in May, it appears that UFC president Dana White will keep the match-up together and instead have the two heavyweight contenders battle later this summer instead.