Two disappointing results on the trot in the league and Europe have brought forward the limitations of the Rangers squad.
Philippe Clement has done well to lift the mood around Rangers since his arrival and is still unbeaten, but there is an understanding that the manager needs help in the winter transfer window.
Rangers are expected to do some incoming business in January and Miller stressed that the need of the hour is wingers.
He feels Clement’s style of football needs quality wide men and while McCausland has impressed, Rangers cannot hope to spend the rest of the season depending on the youngster.
Miller said on BBC Radio Scotland: “It has to be a winger.
“If you want to play this 4-2-3-1 or 4-3-3 you need wingers and Rangers have no wingers.
“Ross McCausland has been the brightest spark tonight but he is still a young lad who has had a handful of appearances.
“You can’t be relying on him.”
Rangers invested heavily in previous manager Michael Beale’s vision in the summer but are expected to spend some money to support Clement in the winter window.