Cantwell joined Rangers in the winter transfer window and was one of the better players in the squad in the second half of last season.
However, like the rest of his team-mates, the attacking midfielder has had a slow start to the campaign and looked lacklustre in the games before the international break.
Ferguson acknowledged the fact that the former Norwich star was very good in the final part of last season but admitted that he needs to do more in the ongoing campaign.
However, he feels Michael Beale is not sure what the midfielder’s best position is and indicated that he needs to play more centrally.
The Rangers legend insisted that Cantwell could be a real game-changer for Rangers this season if Beale can sort out his position.
Ferguson said on the Go Radio Football Show: “The final three months of the season he was very good but I want to see more from Cantwell.
“But I don’t know where his best position is. Is it centrally? Is it on the left side coming in?
“I thought he was more effective last season when played centrally, getting up in support and getting into the box.
“He needs to find a role for Cantwell because I believe if he finds the right role for him, he could be one of the game-changers.”
The 25-year-old and the rest of the Rangers team will look to improve their performances once they return from the international break.
