David McCracken says St Johnstone have performed a U-turn and decided not to offer him a new deal at the club.
The centre-back felt confident that he would be staying at the club and putting pen to paper on a new 12-month contract, but his future has now been plunged into doubt.
McCracken believes the offer was withdrawn because he needed a cartilage operation, but he insists he will be fit for the start of the new season.
"Saints offered me a new deal and we spoke about it. I was ready to sign on but everything seemed to change when I needed surgery," he said in the Sunday Mail.
"I was under the impression we had everything agreed when all of a sudden the contract wasn't there.
"There was a bit of confusion caused by the change of manager when Steve Lomas left and Tommy Wright stepped up but the chairman, Steve Brown, told me the problems at Hearts were a factor.
"I won't be getting offered anything now. They've done a U-turn.
"I know I'll be ready to play at the start of the season so hopefully I'll get something sorted quickly."
New Blades boss David Weir did not rule out the possibility of some young fringe players following the former Toffees coach to United when he recently replaced Danny Wilson as permanent manager of the League One club.
Weir's former colleague at Goodison Park, Under-21s coach Alan Stubbs, said he would seriously consider sending players to team back up with the former Scotland international in South Yorkshire.
"I think it's something that we will think about because it's a big club," Stubbs told Everton's official club website.
"Davey knows the young lads who could benefit the club and benefit him and, if that's the case, and we see if it's right for the player, then why not?
"It will be a great experience for them, but first and foremost we will look and see if it's the right move for the player, because that's what we always do.
"We never send lads out on loan and just leave them. We see if it's the right type of club, whether they play the right type of football, whether it will suit them and whether they will look after the player.
"There are quite a few things we look into before we let the young lads out on loan."
The Ecuador international only showed glimpses of his undoubted talent during his first stint in English football but has excelled since leaving St Andrew's.
He has spent the past couple of seasons in Mexico with Club America and has caught the eye with his performances and prolific goalscoring.
A number of other Premier League clubs are also thought to be tracking the progress of the 27-year-old, with Tottenham among those to have recently been linked with a move.
There has also reportedly been interest from Atletico Madrid in Spain, and his future could soon be resolved.
It is understood that Benitez's agent has flown to the UK for talks with clubs who are considering a move.
