The former Monaco man has struggled to live up to the expectations his blistering first campaign at the club created, but Rush is delighted to see Riise emerging from a frustrating spell on the sidelines.
Rush said: "If there is a positive to take from yesterday, it's good to see John Arne Riise back to form.
"We forget how young Riise is. When he arrived he looked like he was nearly the finished article but he's been the first to admit he's struggled for consistency. Now he's looking confident and lively again.
"If he's learned from his difficult patch, what a great player he could become. He has all the attributes to be an excellent left back. Power, pace, strength and a wicked left foot.
"I'm sure if he ends the season in the form he's showing now, and starts next year just as well, he can quickly establish himself as an indispensable part of the team."