RIO DE JANEIRO – Champ Amanda Nunes knows there will be questions about how much she knows about Raquel Pennington – and how much Pennington might know about her.

After all, Nunes (15-4 MMA, 8-1 UFC) used to train with Tecia Torres, who is Pennington’s (9-5 MMA, 6-2 UFC) fiancee. Now Nunes will put her women’s bantamweight title on the line against Pennington at UFC 224, which will take place May 12 at Jeunesse Arena in Rio de Janeiro. The main card will air on pay-per-view following prelims on FS1 and UFC Fight Pass.

But Nunes said she’s not worried about that training connection.

“I don’t think it matters that much,” Nunes told MMAjunkie earlier this week in Rio. “When the door closes, only me and ‘Rocky’ know what’s going down. We think we know each other, but we don’t know because we never fought before, we never trained together before. It’s going to be a surprise for both of us.

“I know we’re going to be ready, but things are going to happen. Somebody has to win, and I know everything she brings, I’m going to be ready. I did train with Tecia (at American Top Team), and we were close in the gym. But stepping in that cage, no one knows what’s going down.”

Nunes has won six straight fights and hasn’t lost in three and a half years. She took the title from Miesha Tate at UFC 200, then defended it against Ronda Rousey and Valentina Shevchenko.

Now she meets Pennington, who is riding a four-fight winning streak. Nunes is a -450 favorite in the fight – which is the first time since a bout with Shayna Baszler three years ago that won’t be an underdog.

The Brazilian was a slight underdog against Shevchenko both times they fought, and saw her opponent favored when she met Rousey, Tate and Sara McMann. Being a favorite in the UFC is a rare thing for Nunes. But she said she’ll take that in stride, too.

“This is the dangerous thing – I have to be careful,” Nunes said. “MMA is MMA – things can happen. When people underestimate somebody, they get stronger. I’ve been there before. I know how she feels right now, and I’m not going to let that get me down. That’s why it’s going to be good for me this camp, because I know all about what people say. I’m going to worry about me, do my thing, get 100 percent and keep my belt.”

For more on UFC 224, visit the UFC Rumors section of the site.