The Scottish giants are said to have paid a fee of £7m to snare the 21-year-old left-back away from Besiktas in the last summer transfer window.
But Yilmaz has made just four appearances for Rangers across all competitions so far and has failed to dislodge Borna Barisic from the starting eleven.
Ferguson admitted that he is surprised not to see more of Yilmaz given the fact that Rangers paid big money for him and also gave him a five-year contract.
He conceded that sometimes players do need time to settle down but the fee and the contract means Rangers should have got more out of him by now.
The Rangers legend also pointed out that Barisic has not been playing at his best as well and feels it is time the fans see what sort of player Rangers invested in when they signed Yilmaz.
Ferguson said on the Go Radio Football Show: “I am surprised that we have not seen much more of him.
“I don’t know whether he is taking time to settle, he is coming from a different country and he is still young.
“But when you splash that kind of cash, you are expecting, if you are not going to play, at least force your way into the team.
“It looks to me the number one left-back is Borna Barisic, who at this moment in time, is not playing at the level that he had before with Rangers.
“You have got to look at it, why is he not playing? Is he taking time to adapt? That happens.
“The Rangers fans will want to see what he brings to the table in terms of performance levels.”
Yilmaz is already a full Turkey international and has earned six caps for his national team.
