The Ultimate Fighting Championship (UFC) has been having issues locking down main events for the promotion's pay-per-views as of late. In fact, the the last three PPV events hosted by the world's most famous mixed martial arts promotion have suffered last minute changes to their main events. It all started with UFC 221. The event went down inside the Perth Arena in Perth, Australia. UFC middleweight champion Robert Whittaker was initially set to face off against former title holder Luke Rockhold. However, Whittaker suffered a debilitating injury that forced the fighter out of his title defense match up. Rockhold would go on to face Yoel Romero for the interim title. Romero was ineligible for the title, as the fighter missed weight. Still, Romero earned a stunning knockout finish over his opponent. Next up, UFC 222 suffered a similar fate. UFC featherweight champion Max Holloway was initially set to face off against former lightweight champion Frankie Edgar. However, Holloway suffered an injury of his own. Consequently, Edgar would go on to face undefeated fighter Brian Ortega. Ortega shocked the world by becoming the first fighter to ever finish Frankie Edgar. Ortega earned a knockout victory within the first round. Most recently, UFC 223 suffered a last minute change up to the night's main event. UFC interim lightweight champion Tony Ferguson was locked in to fight tough division contender Khabib Nurmagomedov. Only six days away from the fight, Ferguson tore his LCL by tripping over a cable at a recent media event. As a result, Nurmagomedov is now set to take on UFC featherweight champion Max Holloway for the lightweight title. Ferguson's UFC 223 removal made for the fourth time Nurmagomedov and "El Cucuy" have been scheduled to fight and ultimately removed from the their fight card. For more MMA news click here.