McCall was unveiled as the Ibrox outfit’s new man in charge on Thursday after caretaker boss Kenny McDowall left the club.
The former Motherwell manager McCall has been given until the end of the season to turn around the fortunes of the club but he is under no illusions of the task in front of him.
Rangers are 22 points behind leaders Hearts and have only won one match in their last seven games.
But asked if promotion was still possible, McCall said: “Yes, it has to be. Since the defeat to Hearts in November when Rangers could have gone three points behind them at the top, Hearts have gone on and soared.
“Unfortunately our performances and results here have slipped down.
“Confidence is a big thing in football but it’s like any walk of life, if you have confidence you do things better.
“It’s a big, big challenge. Obviously there’s no doubt about that. If anybody has seen the side of late, they will know it is a big challenge.
“But ultimately it is a massive opportunity. It’s a great honour and privilege to come in and try to help the club at this moment in time and something I’m looking forward to.
“I’ve had a million and one text messages wishing me good luck and I will need them all.
“But you only have to look at the players in there. I spoke to them today and they are under no illusions that we have under performed this season.
“But there is enough quality in that dressing room to do better than we have.”