Negotiations for next week's Kamaru Usman vs. Jorge Masvidal UFC welterweight title fight are done, sources said, and both fighters have agreed to terms to compete Saturday at UFC 251 on Yas Island in Abu Dhabi.

That's a massive hurdle cleared for the promotion, which worked to salvage Usman's presence on the card after Gilbert Burns was forced to withdraw Friday night. But it's not the only hurdle left to overcome in an effort to make this fight a reality next weekend.

At the time of this writing, Usman is en route to Las Vegas, while Masvidal, who flew from South Florida to Las Vegas via private jet, landed earlier in the day.

Once in Las Vegas, both fighters must check in to the host hotel, take a coronavirus test and then quarantine while awaiting the results. If they pass the test, they'll be cleared to fly to Abu Dhabi, most likely Monday. If they don't, the fight can't and won't happen.

For the past two months, the UFC and Masvidal were far apart on contract talks to make this fight happen. In the end, the UFC decided to walk away from negotiations about a month ago and gave the title fight to Burns, who recently beat former champion Tyron Woodley.

Afterward, Masvidal posted a series of tweets criticizing the UFC for its business practices, calling into question whether the relationship would be severed for some time. But once Burns was forced off the card late Friday night, momentum started to build for the original plan, which is a grudge match that has been months in the making. Usman and Masvidal have been embroiled in a heated feud that saw the duo get into a shouting match at Super Bowl media row in Miami earlier this year.

On Saturday afternoon, Usman tweeted, "Might be time for the pig to squeal," while Masvidal's co-manager posted a series of Instagram stories showing Masvidal on the phone with the caption "negotiating."

Of course, these days it's not as simple as just agreeing to a fight. Masvidal took and passed a coronavirus antibody test Saturday afternoon. That test shows whether an individual had been exposed to the coronavirus in the past but doesn't determine whether someone currently has the virus. So, at least one hurdle was cleared then. If the fight ultimately gets signed, they'll have to pass three more coronavirus tests before fight night, as will all the fighters competing in Abu Dhabi this month.

Masvidal is considered one of the most popular fighters in the sport, with many believing he was the 2019 fighter of the year after picking up impressive wins over Darren Till, Ben Askren and Nate Diaz. In addition to the welterweight title fight, the card also features Alexander Volkanovski vs. Max Holloway 2 for the featherweight title and Petr Yan vs. Jose Aldo for the bantamweight title.