Ferguson made the revelation during United's current tour of the United States.
It came amid continued uncertainty over Tevez's intentions for the new season following the collapse of a proposed move to Corinthians.
Previously, it was felt United backed off from extending an initial two-year 'loan' for Tevez due to the massive costs involved.
Instead the South American went to Manchester City, where he is thought to be the Premier League's highest-paid player.
However, he has now fallen out of love with the Blues, citing a desperate desire to see more of his wife and two daughters as the major reason for wanting to quit.
In the past, Tevez has spoken of his willingness to retire, which gives credence to Ferguson's words.
However, the 27-year-old forward has distanced himself from those claims and it is suggested he will continue his career for another eight years.
"At no time did he discuss retiring with the Manchester United management and Mr Ferguson has not mentioned this at any time before," a spokesman for Tevez said.
"In fact Carlos feels he is capable of playing for a further eight years and though he has been in the form of his life, he feels he is only going to get better in the coming years."
Ferguson was quoted in The People as saying Tevez told United he intended to play on for only four years when he discussed a contract at Old Trafford in 2009.
Ferguson said: "He told us at the time of negotiations that he was only going to play for four more years, so if we had signed him on a five-year contract knowing that he was going to quit in four years' time, there is no re-sale value for us."