Carney, 24, signed for the Tigers in August on a two-year deal and is one of several new faces in Millward’s squad as they started pre-season training this week.
The coach said: “Justin is a fantastic talent and will be an important asset to our 2013 squad. He badly broke his leg in 2010 when he was on the verge of international selection but he has now regained his confidence and I believe there will be no better winger in Super League next year.
“Like all our new signings, Justin is also a great personality who will really buy in to the community spirit we have at the club so there is no doubt he will be a favourite with our fans.”
He spent the past two seasons with Sydney Roosters, but made just five appearances last term.