For someone who fights as infrequently as UFC welterweight champion Georges St. Pierre, news of his removal from UFC 137 after suffering a knee injury was devastating to MMA fans. Even his dissenters had hoped to see him fight, and possibly lose, to former Strikeforce champion and one-time UFC outcast Nick Diaz in the night’s main event. Any hope of that ended with one tweet from Dana White, 140 characters that would send demand for UFC 137 tickets into an absolute free fall.

UFC 137 Ticket Prices – Before & After GSP’s Injury

The average price for UFC 137 tickets from the time they went on sale in September to Oct. 18, the day White tweeted news of GSP’s injury, was $623. The average ticket price from Oct. 19 to Oct. 26 was $409. That’s a decrease in ticket demand of 34%. Even with St. Pierre’s removal, UFC 137 is still the most demanded event ($588) since SeatGeek started tracking UFC data and the biggest since UFC 126: Silva vs. Belfort ($577.)

Luckily for the UFC, St. Pierre’s withdrawal from the card happened so close to the event’s date that most tickets were already spoken for. Cards headlined by St. Pierre are more in demand than just about anything else, as you can see below.

UFC 137 Tickets: Price Comparison

Overall attendance isn’t so much an issue as the UFC’s bread and butter has never been the live gate. The UFC will be hit hardest by the loss in Pay-Per-View revenue a GSP card reels in. In an interview with Luke Thomas of MMA Nation, Yahoo! Sports’ Dave Meltzer estimated St. Pierre’s absence to have cost the promotion upwards of $8.5 million. A tough pill for a company struggling through a mediocre 2011 marred with underwhelming PPV numbers. It hasn’t helped that Brock Lesnar, St. Pierre’s only true rival in PPV demand, has been sidelined due to illness and hasn’t competed once this year.

A fight between Nick Diaz and B.J. Penn is as good as it gets as patching main events goes, but losing St. Pierre is a killer. While St. Pierre’s title defense to Jake Shields at UFC 129 reportedly generated at least $40 million from about 800,000 buys, experts are predicting UFC 137 to do about half those PPV numbers. Trying to swap a title fight for a quasi contender bout can be done, but there’s no replacement for stardom like St. Pierre’s.