Arturo Vidal
Vidal's future hangs in the balance amid concerns over his knee.

Arturo Vidal's potential move to Manchester United has come under more scrutiny amid suggestions that concerns over the player's knee - thought to be causing the delay in the move - are unfounded.

The Premier League club have been strongly linked with a summer move for Juventus midfielder Vidal as Louis van Gaal continues to prepare a squad capable of challenging for the Premier League title again.

Chile national team manager Jorge Sampaoli recently told El Mercurio, a newspaper in the player's homeland, that an $80m (£47m) move to Old Trafford was in jeopardy because of van Gaal's reservations over Vidal's right knee, which he underwent surgery on in May.

However, a source close to the player has told the same publication United have no concerns over the 27-year-old's long term fitness and will continue to negotiate a fee with Juventus, having already made two offers.

The source told El Mercurio: "The knee is perfect. I don't believe the English club can have so many doubts; they have made two offers and negotiations continue. On this subject, Sampaoli isn't very well informed."

Vidal's participation in the World Cup was initially in doubt when he underwent a procedure to resolve a meniscus injury three months ago. However, the player returned in time to help his country qualify from their group before their campaign was halted by Brazil at the first knock-out stage.

Following his summer break, Vidal returned to training ahead of Juventus' pre-season tour of Indonesia, Singapore and Australia, which got underway this week.

The Bianconeri manager Massimiliano Allegri has previously insisted the club are confident of retaining the midfielder's services beyond the summer and is pleased with his fitness as the new season looms.

"I have spoken with Vidal, mainly about his physical condition," Allegri told reporters.

"Things went well. It would be great if he were to stay at Juventus.

"He is running since yesterday, but we will evaluate day-by-day his condition and when it is best for him to start playing again.

"I am confident that he will be in perfect shape within a week or so."