LAS VEGAS: American Tony Ferguson will step up to take on compatriot Nate Diaz in the main event at UFC 279 after Swedish fighter Khamzat Chimaev missed the weight for Saturday’s welterweight showdown by a whopping 7.5 pounds. The 28-year-old Chimaev tipped the scales at 178.5 pounds, well over the welterweight limit of 171, with his team saying a “medical issue” prevented him from cutting weight effectively. Fighting in the last bout of his UFC contract, the 37-year-old Diaz weighed in at 171, as did Ferguson who was due to meet Chinese fighter Li Jingliang in the co-main event. With Diaz and Ferguson now set to clash, Chimaev will take on Kevin Holland at a 180-pound catchweight, while Li will take on another Californian in Daniel Rodriguez. There was controversy in the build-up to the event as Thursday’s news conference was abandoned after trouble backstage, with Chimaev and Holland getting into an altercation followed by a row between Chimaev and the Diaz entourage. With both sides of that scuffle well represented in the auditorium, UFC president Dana White closed down the news conference quickly, rather than risk an outbreak of violence. The Las Vegas Metropolitan Police greeted people arriving for Friday’s official weigh-ins at the UFC’s Apex building, and UFC officials said there would be a strong security presence at the ceremonial weigh-ins due to take place in the evening.