He even went as far as saying Rashford may have to leave Old Trafford if he wants to become a great goal-scorer.
However, he was adamant that he would not advocate such a move as things can change at United quickly, and the current situation at Old Trafford indicates change might come soon.
In his column in The Sun, he said: “Even if Lukaku did not play, my money would be on Alexis Sanchez being moved into the middle and further forward.
“And would Mourinho really turn to Rashford if he needed another striker? Or would he go to the transfer market for a tried and trusted ready-made goal-scorer?
“Rashford has been played so long in a wide position in a three, that it does take time to re-adjust to his natural position.
“Time is not a great commodity in football nowadays.
“I am not advocating Rashford moves away from Old Trafford. It is a great club to be at.
“But if he wants to achieve an ambition to be recognised as a great goalscorer it is just not going to happen there.
“He would need to move with the assurance that his next club will make him the main man, the striker, the one up top or one of two.
“Then I truly believe he would develop into a goalscorer.”
Rashford was originally deployed as a striker when he was brought out of the academy and into the United first-team by former boss Louis van Gaal in early 2016.
He scored twice on both his United debut and his Premier League debut, as well as once on his England debut, and it looked for all the world that United had found a striker to replace Wayne Rooney and navigate them through the post-Alex Ferguson era.
However, when José Mourinho signed as manager of the club in the summer of that year, he brought in iconic Swedish striker Zlatan Ibrahimović, and moved Rashford out on to the wing.
Due to injury, Ibrahimović did not originally sign a new contract after his one-year deal expired but Mourinho chose to bring in Lukaku ahead of promoting Rashford.
Rashford has not looked out of place on the wing, but he has not been anywhere near as effective as he looked in a central role.
As with many players at United, the key to reigniting his career may be trying to outlast Mourinho.
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