Hauer, who is a new addition to the BBC One show, described the Westlife star as a "winner".
Watch Nicky Byrne's first training session:
"Nicky is a winner already. I just need to fix some little things. He's got what it takes," she said.
"Karen is brilliant, she's really fun," he added.
"She doesn't seem to be losing her head or anything like that. She's very helpful and a great teacher."
The only problem for Byrne was that he came wearing shorts to his first training session and they clashed with his new dancing shoes.
"I was shocked when I had to put the shoes on straight away and I'd worn shorts today because it was quite sunny in Dublin," he said.
"My legs looked the whitest they have been since I was born."
Byrne and Hauer will perform a waltz on the first Strictly Live Shows, which air on October 5 and 6.
Olympian Louis Smith and West End star Denise Van Outen are the current bookmakers' favourites to win the show.
[Strictly promo shows - Photo Gallery]