The former Queen of the South forward arrives fresh from the most prolific spell of his short career. His huge tally helped the Dumfries outfit romp to the Irn-Bru Second Division title and secure the Ramsdens Cup. It also earned him the PFA Scotland player of the year prize for the third tier.
But in the three seasons before last term's goal-laden success, Clark netted just nine times in 86 appearances for Queens and old club Peterhead.
Now Hateley says the 22-year-old must show he is a consistent scorer if he is to succeed at Ibrox.
The former England target man said: "Trying to find a level of consistency will be the most important thing for Nicky. 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."
Clark - like Hateley - arrives at Rangers having followed his father into a career in professional football. Former Portsmouth, Milan and Monaco striker Hateley's dad Tony made more than 400 league appearances in England during spells with clubs including Notts County, Aston Villa, Chelsea and Liverpool.
But he believes Clark must forget about the lessons handed to him by his own father Sandy - a Rangers player between 1983 and 1984 and his coach at Queen of the South - and learn from Light Blues boss Ally McCoist and his new team-mates.
Hateley said: "My dad played during the late 50s, 60s and then early 70s and he taught me how to head the ball, how to mess people around and all that sort of stuff.
"But the game was changing dramatically in that period and when I came in, it was very different. What he taught me was invaluable but then I had to go on and learn from other players and managers."