Kent will be out of contract at the end of the ongoing campaign and he is yet to agree to sign a new contract with Rangers.
Michael Beale is in favour of keeping the former Liverpool winger but so far, there is no agreement between Rangers and the player over a new deal.
The 26-year-old has been one of their better players with nine assists to his name this season and is likely to have offers to move south of the border on a free transfer.
Ferguson pointed out that Rangers will have space on their wage bill next season given the number of players who will be out of contract at the end of the season.
However, he admitted that the structure needs to be broken if Rangers are to hold on to a player of Kent’s quality.
The Rangers legend said on the Go Radio Football Show: “I honestly don’t know their wage structure.
“You have got nine players out of contract and that’s in between £130,000 to £150,000 per week just off the top of my head.
“There is money freed up.
“But I think Rangers will need to break their wage structure if they want to keep a player of Ryan Kent’s quality.”
Beale has stressed the importance of the summer transfer window and he may want to avoid the prospect of replacing Kent.