The Juventus star was named in Chile's 23-man squad for the FIFA World Cup, where they face Spain, the Netherlands and Australia in a tricky Group B.
Vidal underwent surgery at the start of May, but is already back training in a massive boost for Sampaoli's men.
While Sampaoli has been delighted by Vidal's recovery, he remains unsure when the 27-year-old will be available to play.
"Vidal is a footballer who is so far above average in terms of physical and mental capacity," he told a news conference.
"His recovery has surprised me. He's already working with the ball despite the operation.
"But it'll be up to the coaching stuff to decide whether he plays straight away."
Chile face Northern Ireland in a friendly on Wednesday before their first World Cup clash, a meeting with Australia on June 13.
