Timeline: How Oliveira-Chandler vacant title fight came to be

When Khabib Nurmagomedov left the sport as the reigning UFC lightweight champion in October, a vacant title fight between Charles Oliveira and Michael Chandler wasn't on anybody's radar.

Oliveira ranked No. 7 in the division at the time, and Chandler hadn't even made his UFC debut. But here we are, one day away from Oliveira and Chandler meeting in the UFC 262 main event at a packed Toyota Center in Houston to crown a new 155-pound king.

Here's a timeline of the key events that led to an unforeseen title opportunity for Saturday's headliners.

August 2020: Chandler stops Henderson, becomes free agent

Chandler entered his rematch against former UFC champion Benson Henderson at Bellator 243 with one fight left on his Bellator contract. It was known heading into the fight that Chandler planned to test free agency afterward, and he had never done so after spending nearly 10 years in the promotion.

It was a huge fight for the 35-year-old as he would have significantly more leverage if he walked away with a victory. The three-time Bellator champion made the most of the opportunity, knocking out Henderson in the first round and leaving no doubt after beating him by split decision in 2016.

"The future is bright," Chandler said after the win, according to MMA Junkie. "The phone is open, and it's going to be a very interesting next couple weeks. As I said on the mic out there, every single lightweight is on notice right now. Every single lightweight in the top 10 is on the clock."

September 2020: Chandler signs with UFC

A little over a month after Chandler beat Henderson and UFC president Dana White expressed interest in signing him, it was official: Chandler was the newest addition to the UFC roster. His long-awaited signing marked the end of his illustrious Bellator career, which dated back to his fourth professional fight in 2010.

Chandler was briefly linked to a fight against Tony Ferguson at UFC 254 in October, but that matchup didn't come to fruition. Instead, the Sanford MMA product served as the backup for the lightweight title fight between Nurmagomedov and Justin Gaethje.

October 2020: Chandler not needed at UFC 254

Chandler traveled to Fight Island in Abu Dhabi, United Arab Emirates, and took part in UFC fight week festivities for the first time. While he had a rare opportunity to win a championship in his UFC debut, he ended up going home to the United States without adding a fight to his resume. Nurmagomedov and Gaethje both made it to the UFC 254 main event without issue, meaning Chandler's services weren't needed.

October 2020: Nurmagomedov retires

After submitting Gaethje in the second round, Nurmagomedov shockingly announced his retirement as the lightweight champion. "The Eagle" cited his father's recent death and a promise he made to his mother to not compete as the reasons he was hanging up his gloves.

While White was hesitant to consider Nurmagomedov retired for several months, this eventually paved the way for a vacant title fight in one of the UFC's best divisions.

December 2020: Oliveira upsets Ferguson

Oliveira and Ferguson met in a pivotal lightweight bout at UFC 256, the final pay-per-view card of 2020. It was an opportunity for "Do Bronx" to break into the division's top five and for Ferguson to bounce back from his devastating loss to Gaethje earlier in the year.

Oliveira prevailed victorious as a slight underdog, dominating the former interim lightweight champion with his grappling in one of his most impressive showings to date.

The victory moved Oliveira from No. 7 to No. 3 in the lightweight rankings and put him into the title conversation.

December 2020: Oliveira calls for title shot

Along with many MMA fans, Oliveira thought he deserved a crack at the lightweight belt after winning his eighth straight fight.

Oliveira called for a title shot hours after beating Ferguson. He said he specifically wanted to face the winner of the rematch between Poirier and Conor McGregor, assuming Nurmagomedov wasn't returning.

"I have eight wins in a row, seven of those I finish the fights, and I don't let it go to the judges' hands, I finish fights," Oliveira said at the UFC 256 postfight press conference. "I deserve (it), I'm in the position to be fighting for the belt."

January 2021: Chandler stops Hooker in UFC debut

At the end of his second UFC fight week, Chandler made his first walk to the Octagon. There was no warmup fight for the ex-Bellator champ, as he faced off with No. 6-ranked contender Dan Hooker in the UFC 257 co-main event.

Chandler entered his debut as an underdog, but he didn't look like one in the cage. "Iron" finished Hooker with strikes in less than a round and cut one of the best promos ever in his postfight interview, calling out Nurmagomedov, McGregor, and Poirier.

"There's a new king in the lightweight division," Chandler declared.

Chandler became the UFC's No. 4-ranked lightweight with the victory over Hooker. And in the eyes of most fans, he was one win away from a title shot.

January 2020: Poirier sets sights on McGregor trilogy bout

It was widely assumed Poirier's next fight would be for the title after he stunned McGregor with a second-round TKO in the UFC 257 main event to become the No. 1 contender in the lightweight division.

White said a vacant title fight between Poirier and Chandler was the most likely option if Nurmagomedov relinquished the belt. However, Poirier quickly made it clear he wasn't interested in fighting Chandler - and he was even willing to pass up a title opportunity if Chandler was the only opponent available.

Instead, "The Diamond" focused on money fights against McGregor and Nate Diaz, potentially opening the door for someone else - Oliveira? - to get a title shot. The UFC has since booked a highly anticipated trilogy bout between Poirier and McGregor for the UFC 264 main event in July.

March 2020: Nurmagomedov vacates title, UFC books Oliveira-Chandler

With Poirier in talks to face McGregor for a third time, Oliveira and Chandler were left as two of the most likely candidates to take part in the next championship bout.

Moments after White announced Nurmagomedov had officially relinquished the lightweight title, it was revealed that Oliveira and Chandler would do battle in the UFC 262 main event on May 15 to crown a new champion and kick off a new era in the division.