The Australian-born Great Britain international will join Leeds next season on a one-year deal, which Sinfield was involved in arranging during his final days at the club.
Sinfield left Rhinos last Sunday to join the coaching staff at rugby union giants Leicester Tigers, but predicted Austin “will be a success”.
Sinfield said: “I worked with him a little bit at Great Britain and in all my dealings with him, he has been an outstanding individual.
“He understands the role, Rich [Agar, Rhinos’ coach] has chatted that through with him and he understands the size of the club.
“The great thing about him is he is an out and out runner, it doesn’t matter where he pays because he is going to run and he is going to scare people to death.”
Austin has played in the halves for Warrington, but Sinfield stressed: “He is coming in as a utility-player and he knows that.”
He added: “He will cover at full-back, centre, in the halves and maybe a bit at loose-forward.
“I do know a couple of NRL clubs had a similar plan for him, if they signed him, but we got in early and got him first.”
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