There's little doubt that the indefinite departure of Georges St-Pierre will leave a big hole in the UFC's pay-per-view business.

During his nine-plus years and 15 career main event fights, events that St-Pierre has headlined have drawn approximately 10,145,000 pay-per-view buys. A figure which would be more than any MMA fighter in history.

In 2013, he was responsible for what are estimated to be the two biggest shows of the year. His March 16 fight with Nick Diaz did approximately 950,000 buys. UFC 167, held on Nov. 16, where he defeated Johny Hendricks in what was the most talked about decision of the year, is currently estimated at doing 600,000 to 650,000 buys, a number significantly above what Manny Pacquiao vs. Brandon Rios did a week earlier. While not as big in the United States, the latter show reportedly set records for any type of pay-per-view in Eastern Canada, where St-Pierre is from, and also reportedly set a UFC record with more than 40,000 fans across the U.S. watching in movie theaters.

The number for the Hendricks fight would be a disappointment because it would be the lowest for a St-Pierre card since 2008.

Numbers for the pay-per-view industry as a whole have been below expectations since September, after the Floyd Mayweather Jr. vs. Canelo Alvarez show did an estimated 2.2 million buys, and set a revenue record, generating in excess of $150 million.

If St-Pierre doesn't fight next year, it will likely greatly impact the company's pay-per-view business, but the company in recent years lost Chuck Liddell and Brock Lesnar, and this year was still its best year on pay-per-view of the last three.

UFC has, what on paper should be its biggest pay-per-view of the year on Dec. 28 with the double headliner with rematches of Weidman vs. Silva and Ronda Rousey vs. Miesha Tate. The event has sold out the MGM Grand Garden Arena and will become the third show in company history to top a $6 million live gate. A location on the MGM Grand premises was opened up this week for closed-circuit showing.

UFC President Dana White has stated many times that he believes this will be the biggest pay-per-view show in company history, although few believe the momentum is there at anywhere near the level going into UFC 100 in 2009, the company's high point. As St-Pierre vs. Diaz showed, the difference between good and great numbers on pay-per-view is the final week hype and momentum.