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UFC champ Rose Namajunas says she wouldn't rule out a superfight against Valentina Shevchenko ... but first, she's gotta get through Jessica Andrade.

Rose is the reigning UFC strawweight champ (115 lbs) after posting two amazing wins over UFC legend Joanna Jędrzejczyk.

She's gearing up for a title defense against Andrade this weekend at UFC 237 -- and despite being the champ, Rose is the betting underdog going into the fight.

"It's definitely a familiar feeling. This is not something new. I'm always the underdog. Not always, I shouldn't say that, but generally speaking," Namajunas told us.

"And, it makes sense. Andrade, when you look at her highlights, when you look at her physique, and you look what she does to girls, it's pretty intimidating."

Andrade's a beast ... but if she wins, would Rose -- who's cleaned out her division -- go up a weight class and fight the 125 lb. champ, Shevchenko?

"I've trained a lot with Valentina. Definitely, the training sessions, the way she trains, she's an animal. Of course, I'd love to test myself against her."

The issue? They're friends ... but Thug Rose ain't above punching her buddies.

"She's also my friend too, so that would kinda be strange. But, it's whatever, like I've fought friends before multiple times."