MacDonald vs. Lombard Off, Mighty Mouse vs. Horiguchi New Co-Main at UFC 186

UFC 186 just added a little more shine to its lineup. 

According to the UFC, the originally scheduled co-main event between top-five welterweights Rory MacDonald (18-2) and Hector Lombard (35-4-1, 1 no-contest) has been called off due to unknown circumstances. The press release said "updates for both fighters will be provided when available." 

Sliding into this co-headlining slot on April 25 in Montreal is a flyweight title fight between the champion, Demetrious "Mighty Mouse" Johnson (21-2-1), and his challenger, Kyoji Horiguchi (15-1). 

Johnson is the only flyweight champion in UFC history. He first won the belt in September 2012, earning a split-decision victory over Joseph Benavidez (21-4) at UFC 152. Since then, he's defended his strap five times, establishing himself as the clear-cut No. 1 flyweight in the world in the process.

He's finished three of his five title defenses, and his two decisions were unanimously decided in his favor.

To his credit, Horiguchi has looked phenomenal since coming to the UFC in October 2013.

The Japanese standout is 4-0 inside the Octagon, finishing half of his bouts via TKO and generally dominating his competition along the way.

Against Mighty Mouse, he's facing a different animal than the likes of Louis Gaudinot and Darrell Montague, but he's proved himself a worthy challenger throughout the course of his 16-fight professional career.

Interestingly enough, Johnson recently told Ariel Helwani of The MMA Hour, via Marc Raimondi of MMAFighting.com, that he'd fight UFC bantamweight champion T.J. Dillashaw (11-2) for the low, low price of $2 million.

Dillashaw headlines UFC 186 in a rematch against Renan Barao (33-2, 1 no-contest), so if both Johnson and Dillashaw notch victories on the evening, we may hear these "superfight" talks heat up a bit during the post-fight press conference. 

With this switch-up, the UFC 186 card now looks like this: 

Fighter	Opponent	Weight Class	Notes
T.J. Dillashaw (c)	Renan Barao	Bantamweight	For the UFC bantamweight title
Demetrious Johnson (c)	Kyoji Horiguchi	Flyweight	For the UFC flyweight championship
Quinton "Rampage" Jackson	Fabio Maldonado	Light Heavyweight	Jackson makes UFC return after 27-month absence
Michael Bisping	CB Dollaway	Middleweight
Yves Jabouin	Thomas Almeida	Bantamweight	Almeida puts 18-0 record on the line
Patrick Cote	Joe Riggs	Welterweight
Chad Laprise	Bryan Barberena	Lightweight	Laprise looks for second win since winning TUF Nations, brings 10-0 record to the Octagon
John Makdessi	Abel Trujillo	Lightweight	So much violence
Olivier Aubin-Mercier	David Michaud	Lightweight
Nordine Taleb	Claudio Silva	Welterweight
Jessica Rakoczy	Valerie Letourneau	Women's Bantamweight	Rakoczy fights for first time since losing at TUF 18 Finale in 2013.

Do you think Horiguchi has a chance against Johnson, or will this be another relatively stress-free title defense for the 125-pound king? 

Stay tuned to Bleacher Report for updates on MacDonald and Lombard as details are released.