Julianna Peña is not happy about Amanda Nunes' retirement.

Immediately after Nunes laid her gloves in the Octagon after her win over Irene Aldana at UFC 289 on Saturday, Peña took to social media to express her frustration over the sudden announcement.

Peña and Nunes were originally slated to main event UFC 289 before Peña had to pull out of the bout due to broken ribs suffered in training.

It was Peña who surprised the world by ending Nunes' six-year undefeated streak by choking her out at UFC 269 in December 2021. Nunes responded by defeating Peña to regain her UFC women's bantamweight championship in July 2022, which set the two up for a rubber match scheduled for this weekend.

Instead, it seems like Peña's ill-timed rib injury will leave fight fans wondering what if.

"I was supposed to beat her tonight again," Nunes said, per Marc Raimondi of ESPN. "If it was Julianna Peña tonight, I wouldn't retire. I wanted to fight somebody I never fought before and then retire."

Nunes, who turned 35 last month, could ultimately decide to pull back on her retirement. She would not be the first, nor would she be the last fighter to decide that "retirement" means more of a short-term break. UFC president Dana White said he "absolutely" wanted Nunes, the most dominant female fighter in MMA history, to stick around.

For now, though, Nunes appears committed to her UFC exit. She said she plans on shifting her focus to her Florida-based training gym in retirement.

"I have my gym," Nunes said. "I have a couple girls there. I'd love to help them to be able to see [MMA achievements], as well. I have a lot to offer. As a double champ, I know a lot. ... I'll be able to make a girl champion, too. If I really work with one girl, I can make her a champion. I know everything about this game."

Nunes retires with a 23-5 overall record, which includes a UFC women's record 16 victories in the promotion.

Peña, who is 11-5 as a professional, would likely be at or near the front of the line to fight for a vacant women's bantamweight championship if Nunes follows through with her retirement.