The implication was that Keane, who was officially omitted from the Ferguson’s 23-man squad because of a hamstring injury, had actually been left out for disciplinary reasons.

Ferguson has refused to comment on the speculation and club officials remained tight-lipped this afternoon when the United party flew into China fo the second leg of their four-match tour.

Instead, Keane’s long-time adviser Michael Kennedy has responded on his client’s behalf.

And while there is no denial of an argument with Ferguson, the suggestion that it resulted in Keane being forced to stay at home was flatly rejected.

“The allegation that Roy Keane was left out of the club tour of Asia because of a row with his manager is completely without foundation,” said Kennedy.

“He remained in Manchester in order to continue his treatment for a hamstring injury. Any disagreement he may have had with his manager is a private matter and will not be the subject of comment by him in the media.”

Ferguson is due to attend a press conference to promote Tuesday’s encounter with Beijing Hyundai tomorrow lunchtime, when he is likely to be quizzed about the issue further.

Whether the Scot will decide to enter any public debate is another matter given his previous reluctance to divulge information he deems to belong to the sacred sanctity of the dressing room.

Given the esteem with which he holds Keane, the suggestion Ferguson might prevent him being part of a tour which is such a vital part of United’s pre-season programme always appeared a little odd.

Throughout his 12-year Old Trafford career, the influential 33-year-old midfielder has always been one of Ferguson’s allies.

In recent times, the Scot has even adjusted United’s tactics to take some of thepressure off his captain, while he has also suggested he could replace him as Red Devils manager at some stage.

However, it is becoming apparent the pair did not share the same philosophy over United’s trip to Portugal.

In an effort to avoid the early season stumble which wrecked last season’s title challenge, Ferguson called his squad back a week earlier than usual, but with training on the Algarve restricted to half-daily sessions, the United boss decided to let wives and children accompany his squad for the duration of the week-long stay.

It seems the move did not go down well with Keane, who famously stormed out of Ireland’s World Cup preparations in Japan three years ago after voicing sustained complaints over Mick McCarthy’s training methods and the facilities available.

Ferguson’s attention to detail is such that Keane is highly unlikely to have found any issue over the training complex itself. But what is likely to have annoyed the United skipper is attention being diverted away from preparations for the new season.

After two successive failures in the Premiership and Champions League, the notoriously single-minded midfielder felt the Old Trafford squad should have been concentrating their energies solely on training – and is thought to have told Ferguson so in a typically frank manner.

Given the combustible nature of both characters, the response is likely to have been equally forthright, but it woud be a major surprise if either allowed the row to rumble on any further.

Despite occasional disagreements, the pair have always been close and the United manager rarely misses an opportunity to remind the world how important Keane is to his plans.

It is understood Keane was troubled by a hamstring problem on the Portugal trip and his absence from the squad was initially confirmed in Hong Kong a week before departure.

Ferguson clouded that issue himself almost immediately by stating there was still a chance Keane would be involved, although even at that point, it is thought the player knew he would definitely not be involved and would instead remain at home along with Wes Brown and Gabriel Heinze to work on his fitness ahead of the new season.