UFC and ONE Championship recently made a historical trade between promotions, a first for this modern age of mixed martial arts, when ONE sent their welterweight champion Ben Askren for the UFC's former pound-for-pound king in Demetrious 'Mighty Mouse' Johnson.
With high profile athletes swapping sides, we look at five other fighters from other promotions who can enter the world's premiere MMA organization in the UFC.
(Note: We will not be listing fighters who have already appeared officially for the UFC.)
Michael Chandler - Bellator
As Bellator were possibly preparing for the departure of Eddie Alvarez, the promotion would look to a new marquee name to build their brand around. Michael Chandler, the man that dethroned Alvarez for the lightweight title, would be that man.
After defending his title for the first time in 2013, Chandler re-signed with the promotion with an eight-fight deal, the first of Chandler long-term contracts with the company.
Chandler also received the "Alvarez treatment" in Bellator, showcasing against worldwide marquee talent in non-title main event bouts.
Other than splitting a pair of fights with Alvarez, losses to former UFC veteran Will Brooks, plus a freak injury against Brent Primus, Chandler would cement his name as one of Bellator's top fighters. The Nashville resident holds notable wins over Benson Henderson, Patricky Pitbull, David Rickels, Rick Hawn, Brandon Girtz and Marcin Held.
Chandler was a former NCAA Division 1 All-American wrestler with multiple knockouts on his record. This skill-set would cause fits for ranking members of the UFC's lightweight division.
Unfortunately, as Eddie Alvarez exited the promotion and ventured to greener pastures in ONE Championship, we will unlikely get to see the rubber match between Alvarez and Chandler in the UFC.
Honorable Mentions - Douglas Lima, Fedor Emelianenko, Patricio Pitbull
Mamed Khalidov - KSW
The most dominant middleweight outside of the UFC, Mamed Khalidov has spent majority of his career fighting in Poland for Konfrontacja Sztuk Walki (KSW). Khalidov began fighting for the KSW in 2007 and it has remained his main promotional home since then.
Khalidov earned the KSW light heavyweight title in 2009, and followed up winning the middleweight title in 2015. Khalidov was undefeated in the promotion until March 2018, losing to current KSW light heavyweight champion Tomasz Narkun in a catchweight bout.
Khalidov built up his star power in Poland to an extent in KSW that the promotion would bring in notable fighters from across the world for Khalidov to showcase against in the main event of some of their cards. Khalidov has defeated the likes of Matt Lindland, James Irvin, Melvin Manhoef, Maiquel Falcao, Jesse Taylor and Brett Cooper.
Khalidov allegedly received offers from UFC in 2012, but turned down the contract due to 'financial matters,' according to an interview with ValeTudo.ru.
Honorable Mentions: Michal Materla, Tomasz Narkun, Mateusz Gamrot
Bibiano Fernandes - ONE Championship
With ONE Championship recently acquiring former UFC champions Eddie Alvarez and Demetrious 'Mighty Mouse' Johnson, there may be cause for concern for ONE's champions going the other way. Even with multiple dual-division champions, and marketable stars at their disposal, there is still one single dominant champion remaining in ONE's ranks, bantamweight honcho Bibiano Fernandes.
Fernandes first appeared for ONE Championship in 2012, winning the interim title in his next fight with the promotion in May 2013. 'The Flash' unified the title after defeating Soo Chul Kim that October. Fernandes would defend the title a total of seven times.
In his latest fight, Fernandes went up against two-division champion Martin Nguyen, who was attempting to win a third title in his third weight class. Fernandes took a split decision to retain his title and derail the up-and-coming star.
Fernandes spoke with MMAFighting following his successful title defense and the heavy promotion of his opponent attempting to make history, “I have eight title defenses, and in my opinion, they want to end that. They want someone to take me down at any cost, They thought ‘this guy, a heavier fighter with heavy hands, long reach, will definitely beat Bibiano.’ They definitely thought he would beat me, but it didn’t go the way they hoped. They were ready for him defeating me."
The UFC courted 'The Flash' in the past, previously announcing they signed the bantamweight superstar in 2012. Fernandes was reportedly to debut at UFC 149 in Calgary, but withdrew due to injury. Fernandes spoke with media saying he was in negotiations with UFC, but never actually signed with the promotion.
Fernandes would not have issues finding high quality opponents at the top of the division with Dominick Cruz, Marlon Moraes and Raphael Assuncao looking for a crack at the title.
Honorable Mentions: Angela Lee, Martin Nguyen, Shinya Aoki, Aung La Nsang
Ray Cooper - PFL
At the start of 2018, Ray Cooper III was just a second-generation mixed martial artist entering the inaugural season of Professional Fighters League in an attempt to win the $1 million tournament. By the end of the year, Cooper was not only a finalist, but was the number-one seed in his division.
Cooper only spent eight minutes and five seconds of cage time en route to the PFL finals.
Another interesting fact, Cooper stopped Jake Shields twice in the tournament. Shield previously defeated Cooper's father in 2004.
Cooper seems to be one of PFL's new draws in addition to fighters built up in the World Series of Fighting era.
Honorable Mentions: Lance Palmer, Kayla Harrison, Louis Taylor
Paddy Pimblett - Cage Warriors
The most notable featherweight to come out of Cage Warriors since Conor McGregor, Paddy Pimblett has been receiving comparisons to the Irish star since winning the featherweight title in 2016.
Though Pimblett had failed in his attempt to claim a second Cage Warriors title in a second weight class, Pimblett is still one of the prospects that the European-based promotion tries to get behind.
During Pimblett's winning streak in 2016, Irish bookmaker Paddy Power put out a £2,000 bet which would pay out at 5/1 if Pimblett were to face and defeat Conor McGregor by 2020.
Frequently, Cage Warriors would book Pimblett to fight in front of his home crowd at Echo Arena in Liverpool, much like McGregor in Dublin. Unfortunate fighters who have defeated Pimblett in Liverpool were rained down with garbage and coins following their fights.
Pimblett would spurn offers from UFC after winning the Cage Warriors featherweight title, and more recently rejected an offer to fight at UFC's first event in Liverpool.
Honorable Mentions: Mauro Cerilli, Soren Bak, Ross Houston