5 blockbuster UFC rematches that will likely never happen

#4. Conor McGregor vs. Jose Aldo (UFC 194)

UFC 194: Jose Aldo vs. Conor McGregor

Conor McGregor's 13-second knockout of Jose Aldo was arguably the most important fight of the Irishman's UFC career. The UFC 194 showdown between the long-reigning featherweight champ and white-hot interim titleholder was the moment that launched McGregor's career into the stratosphere.

Taking nothing away from McGregor's incredible performance, not much can be proven in a fight that ended after only a few seconds. So why hasn't there been a rematch?

It's reasonable to assume that the UFC was protecting McGregor, who was a money-printing machine for the promotion. There's no reason to believe McGregor wouldn't beat Aldo for a second time. However, the Brazilian has proven time and again that he's one of the most consistent contenders on the UFC roster and putting him against the Irishman is just too risky of a business move.

Aldo reclaimed the featherweight strap before losing it to Max Holloway, but his second chance against 'The Notorious' never came. Presently, the two are separated by two weight divisions after McGregor climbed to lightweight and Aldo dropped to bantamweight. For that reason alone, it's highly unlikely that they'll meet again inside the octagon.

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#3. Amanda Nunes vs. Cris Cyborg (UFC 232)

UFC 232: Cris Cyborg vs. Amanda Nunes

For a time, the GOAT debate for women's MMA revolved around UFC champs Amanda Nunes and Cris Cyborg. In one of the biggest dream matches in UFC history, the Brazilian warriors finally collided with the featherweight title on the line.

Coming in as a +200 underdog, Nunes shocked the world when she outstruck the more physically imposing Cyborg with under a minute left in round one. In doing so, the 'Lioness' became the first-ever female champ-champ in the UFC, a distinction that she still holds today.

Nunes has gone on to make four consecutive title defenses and solidify her status as the undisputed women's GOAT of the UFC. Cyborg, meanwhile, returned to winning ways after bouncing back with four straight wins, including her final fight in the UFC and her first three outings in Bellator MMA.

Given that Nunes and Cyborg are in two separate promotions, a rematch between the two Brazilian icons is likely out of the equation.