Prior to her defeat at the hands (and feet) of Holly Holm, the Ronda Rousey matchup that most fans had been clamoring for was with Cris "Cyborg" Justino.
Cyborg is a Brazilian fighter who hasn't lost in 10 years, racking up a total of 15 wins (although one was overturned due to her use of a banned substance). Even more impressively, 13 of those wins came by TKO, many of them in the first round.
In 2009, she pounded WMMA pioneer Gina Carano into retirement, before becoming an undefeated champion in both Strikeforce and Invicta FC. In short, she's one scary fighter, and has spent the past decade destroying all of the competition outside of the UFC.
While she and Ronda Rousey fight in separate weight classes (Cyborg is at 145, while Rousey is at 135), a catchweight matchup between the two of them was one of the UFC's most common fan requests. It even sounded like it might be happening in 2016, with rumors of Cyborg making adjustments in her training to lose the weight necessary to challenge Rousey for the UFC bantamweight title.
Unfortunately though, that fan-dream has just been shattered. In the aftermath of Rousey's loss to Holly Holm, Cyborg has announced that she's no longer interested in pursuing that matchup.
Instead of dropping weight to enter the UFC's bantamweight division, she's opted to instead stay at 145 and defend her Invicta title. She's agreed to a bout against Daria Ibragimova at Invicta FC 15 in January, which will air live on UFC Fight Pass.
This decision does make some amount of sense. Slimming down an entire weight class would be very difficult for most fighters, and doing so without getting a shot at the title would make that route even less appealing.
However, there's still some hope. Cyborg's management have confirmed that she'll take the fight with the Rousey if offered, but only if she doesn't have to drop drown to 135lbs.