"It's a side of her that we haven't really seen," Harding told TooFab. "I've never really seen her dance in public, so I think that can be a good showing off of her talent."
"There's something so classic about her," he said. "I feel like she could really rock it in like a classical sort of jazz or ballroom, but I bet hip-hop could be something that she could excel at."
Harding admitted he hasn't watched the ABC reality competition in a "very long time" because he's been "under a rock for a while."
"I'm trying to get off social media as much as possible," he explained. "And then next thing I know it's my birthday and people are like, 'It's your birthday.' And I'm like, 'Yes, it is. That's right.'"
TooFab learned that Pieterse will kick off Monday's preimere episode of Season 25 dancing the Cha Cha to Fleur East's "Like That" with her partner Gleb Savchenko.
"It's a Latin American dance, it's fun, it's cheeky, it's pretty fast," Savchenko told TooFab at a pre-Emmys event on Thursday. "We're working a lot on the technique and the stamina, so that's like the two major things I'm focusing on right now, but the dance is done, so we just keep running it."
Savchenko choreographed this week's performance to mirror what he knows of Pieterse's personality thus far.
"She's amazing. She has a great natural rhythm. She's not a dancer, though," he said. "She doesn't have any dancing experience, but she's very talented. You know, when you're talented, I feel like you're talented in everything, and she works really hard. Even though she's only 21, she's very mature for her age and she wants to learn how to dance."
"Dancing With the Stars" premieres Monday night on ABC.