As reported by Chilean paper El Mercurio (h/t Matt Morlidge of the Daily Mail) Sampaoli suggests the new United manager isn't comfortable with dropping a large sum on the player while he continues to battle through injury.
"I know that the main problem in Vidal's $80m (£47m) transfer from Juventus to Manchester United is Louis van Gaal's doubt over the improvement of Arturo's knee," said Sampaoli. The national coach also indicated Vidal was playing at "30 or 40 percent" during the 2014 World Cup, where his willingness to battle through the pain was obvious.
Such a situation throws up something of a dilemma for Van Gaal. United fans are craving the box-to-box midfielder's arrival, especially after a summer of speculation. While the new boss will want to land a marquee signing during his first transfer window at the club, it is risky to drop the reported £47 million on a player who is yet to prove his knee has healed since Chile's exit from the World Cup.
Van Gaal is also known to be courting Roma's Kevin Strootman, whose status is similar to Vidal's. The Dutch midfielder is set to return to competitive football at the start of next season after being injured in March, but Van Gaal has hinted he isn't ready to commit until the 24-year-old proves the damage to his cruciate ligament is repaired.
"Strootman I can judge, but he has been injured for more than six months," said Van Gaal, per Sky Sports. "We have to wait and see how he comes back. It's not so easy to come back out of an injury, so we'll wait and see."
Should Manchester United sign Arturo Vidal even if he isn't fully fit?
The financial difficulty here becomes more apparent when you consider United's potential battle against UEFA's Financial Fair Play rules. Should Van Gaal snap Vidal up and qualify for the Champions League during his first season, the governing body will inspect United's ability to break even next campaign.
Finances from 2014-15 will be included in this, meaning the club could effectively throw away a large part of their transfer kitty if Vidal comes and doesn't play. Worse still, the Red Devils would be inspected if they qualified for the Europa League, a potential double whammy if Vidal was ruled out and United weren't receiving the lucrative payments of the Champions League.
The club simply cannot afford to take this risk when an estimated £30-£70 million isn't being made due to the lack of a European appearance this season, per ESPN. Van Gaal has the transfer money to deploy, there's no doubt about that, but he would be foolish to land the superstar midfielder if his knee continues to be a problem.
Juventus boss Massimiliano Allegri will certainly be pleased if United's interest waned. The new manager needs to ensure his squad make the transition away from Antonio Conte's successful era with aplomb, meaning he will need Vidal and Paul Pogba in the heart of midfield.
"Vidal and Pogba are delighted to be here and I am delighted to coach them," said Allegri, per Morlidge.
A similar situation to Strootman's is likely to take shape, with United waiting it out until January before attempting to land their man.
Van Gaal is set to make decisions on his squad in the coming days, as reported by United's official website. He will be pleased with the side's successful run in the International Champions Cup, which saw the new boss deploy his 3-5-2 formation to devastating effect. That said, United's midfield of Ander Herrera and Darren Fletcher could certainly be improved with a destructive alternative.
Vidal's potential move may die out without further acknowledgement if Sampaoli's words ring true. Van Gaal isn't the type of manager to risk a momentous sum on one player who may not be firing at 100 percent.
However, if Vidal proves his fitness during Juventus' current tour of Asia, we can expect the rumours to multiply once more.