"It's really exciting news for Phoenix and Patrick as they embark on this journey together and the Mystics family send their best wishes to them both," she said.
"Phoenix has taken great strides since taking on the captaincy role over the last two years, and her leadership has played a big part of our success this season.
"We know she will be supporting the club no matter the role and we look forward to meeting the newest member of the Mystics whānau."
Karaka, who made her international debut in 2014 and has 30 Test Caps, was a member of the Silver Ferns team which won the Netball World Cup in Liverpool last year, and coach Dame Noeline Taurua said she was delighted to hear the news.
"Phoenix had an outstanding season last year which led her on a special journey to a Silver Ferns recall and a Netball World Cup title," Taurua said.
"Now she and Patrick are about to experience another special and exciting journey, and I send my best wishes to them."
Karaka, who plays both in-circle defensive roles, captained the Mystics to third place in this year's ANZ Premiership.