Clark has faced a viewer backlash throughout the competition and sparked a scandal when he was saved over Carolynne Poole last week, but the pair told journalists including Digital Spy that they see the model as "a serious contender".
"People [think] Rylan is really eccentric, but he's really down to earth," Douglas stressed. "He's actually quite a serious contender.
"I think Rylan can switch it up. I've heard some of his stuff on YouTube and he's great. He's fooling all of you, he can sing. I think it's good to hold back in the first few weeks, then build up [support]."
When Sones was asked who he saw as his biggest competition, the former chimney sweep replied: "Probably Rylan. I though Rylan did wicked last week.
"I was shocked to see him in the bottom two. I thought his performance was wicked, I thought he smashed it."
Sones also insisted that Poole's elimination had not affected their mentor Gary Barlow, who stormed out of the studio when Clark was saved.
"I think [the walk-out] just shows how much he actually cares," Sones said. "It's not just a Saturday, Sunday job for him.
"All the contestants in the Overs he's very passionate about, so I think that just shows how passionate he was."
The X Factor continues tomorrow (October 13) at 8.20pm on ITV1.
New! Digital Spy breakfast show - watch Daniel Sperling discuss the day's biggest stories including Rihanna's next album, Quentin Tarantino's Django Unchained and The X Factor's Rylan: