LAS VEGAS — Antonina Shevchenko’s primary job this week is as a training partner. Her sister Valentina is fighting Amanda Nunes for the UFC women’s bantamweight title Saturday night at UFC 213 here at T-Mobile Arena.

But by Sunday, the other Shevchenko sister will likely move to the forefront in the practice room. Shevchenko will fight in MMA for the first time since 2005 in September, she told MMA Fighting on Thursday at UFC 213 media day.

Shevchenko said she is fighting Kerry Hughes for Phoenix Fighting Championship on Sept. 22 in London. Shevchenko has one MMA fight on her record, a unanimous decision win 12 years ago in South Korea. Her main focus throughout her combat sports career has been on Muay Thai and kickboxing.

There was a time Shevchenko was unsure about MMA, but after consulting with longtime coach Pavel Fedotov, this is the route she is now going.

“The promotion, they just offered me a fight,” said Shevchenko, who like her sister splits time between Peru, Thailand and the U.S. “Our coach was thinking about it and we just accepted it. It doesn't mean I will not fight Muay Thai.”

The plan, Shevchenko said, is to take the fight in London and then return to the United States to defend her Lion Fight Muay Thai title. Shevchenko, 32, isn’t worried about potentially ever having to fight Valentina in the UFC, because she believes ultimately Valentina’s future is at flyweight. The elder Shevchenko said she can’t really speculate too much, because she’s not in the UFC yet.

“I cannot say about this right now, because I have to start with my MMA fights,” she said. “But I think there is now a 125 division and that is more better for Valentina. She was already 135 like two months ago.”

Shevchenko was alongside her sister — as she almost always is — at media day Thursday. There has been some tension between Valentina and Nunes leading up to this fight. Nunes put her fist on Valentina’s face during a staredown in May and shoved it. Some harsh words have been exchanged between the two.

But Antonina is not worried about her younger sister’s mindset going into Saturday night. Not at all.

“It’s not a big deal,” Antonina said. “The big deal is the belt, I think. She wants this belt. That’s why she’s more concentrated for it. … Usually, of course, for every fight she’s completely concentrated. Every fight is a step. It’s a step to the belt. if you don’t go through these steps, you don’t get the belt.”

Perhaps Antonina Shevchenko will be talking about her own MMA title fights before long. She is a multiple time Muay Thai and kickboxing world champion, a southpaw like her sister and even longer and rangier.

Antonina is not 100 percent ready to concentrate fully on MMA just yet, though. In the interim, she’ll remain a multiple combat sports athlete.

“For now,” Antonina said, “I’ll do both.”