It may be a result of the UFC's new, comprehensive health insurance plan for their fighters, or it may just be bad luck - either way, the promotion has had to deal with one headache after the next as main events continually fall through due to injury.
The most recent hit came in the form of a knee injury to UFC welterweight champ Georges St-Pierre, which drove the French-Canadian superstar out of his planned title defense against Carlos Condit just over a week before the two were scheduled to fight. At this point though, the promotion is well-suited to dealing with unfortunate main event cancellations, this being the seventh match with top billing that they've had to reschedule and replace this year.
It started with UFC Fight for the Troops 2 in January, when Kenny Florian pulled out of his match-up with fellow lightweight contender Evan Dunham after suffering a knee injury; Melvin Guillard stepped up in Florian's place and won the event via knockout.
Next, UFC 128 in March saw a light heavyweight title fight between then-champion Mauricio "Shogun" Rua and Rashad Evans fall through when Evans injured his knee in training, opening the door for Jon Jones to step in and take the light heavyweight title on short notice.
Later in March, a light heavyweight bout between Tito Ortiz and Antonio Rogerio Noguiera scheduled for the main event of UFC Fight Night 24 was scrapped when Ortiz suffered a deep cut in training. Young contender Phil Davis was brought in and took home what still stands as the biggest win of his young career.
In May, the lightweight rubber match between champion Frankie Edgar and Gray Maynard was scrapped from the top-slot of UFC 130 and replaced by a light heavyweight tilt between Quinton "Rampage" Jackson and Matt Hamill when Edgar and Maynard both sustained injuries during camp.
UFC 131 went down in June and was supposed to feature a heavyweight match between The Ultimate Fighter 13 coaches Brock Lesnar and Junior dos Santos, but Lesnar was forced out after suffering a flare-up of diverticulitis and replaced by Shane Carwin.
Rounding out the tally is UFC 133, which went down in August and had a light heavyweight contender's match between Rashad Evans and Phil Davis cancelled when Davis injured his knee in training. Former light heavyweight champ Tito Ortiz filled in for Davis against Evans on short notice, and would go on to lose to Evans via second round knockout.
Imagine, had any of those originally-scheduled fights actually occurred, how different the MMA landscape could look depending on their outcomes. Just approaching November and with six scheduled events left to run through after UFC 137, the UFC could still - and likely will - encounter their fair share of main even hang-ups before year's end.