Clark's 41-goal tally helped Rangers runaway with the Second Division title, and also earned him the PFA Scotland Player of the Year prize.
And former Ibrox striker Hateley says the 22-year-old must show consistency if he is to succeed under Ally McCoist.
"Trying to find a level of consistency will be the most important thing for Nicky," Hateley said.
"That is the most challenging thing for any young player at any club. When you go to a big club, it's even more demanding.
"He got 40-odd goals last season. But what did he get the year before? One.
"Consistency is everything. He had a great year last year but I would suggest he is coming to a better club than he played at last year, that will make more chances for him and it's all about having that self-belief to put the ball in the back of the net."