Valdivia, known as "The Magician" in Chile, made his entrance after an hour, with his side 1-0 down. Five minutes later they equalised through Alexis Sanchez, and Valdivia was at the heart of many of their best moves from then on.
"Jorge changed the rhythm when he came on. He's the one who dictates the pace of the game and it was noticeable yesterday," Vidal said. "The goal that Alexis scored came from a ball from Valdivia."
Valdivia, who plays his club football at Palmeiras in Brazil, is one of Chile's most gifted playmakers but has been plagued by injuries, both at last year's World Cup and at this tournament.
He was sidelined for Chile's Copa America opener against Mexico, but appeared to be back on form against Uruguay.
"I've been watching Valdivia since he was 17, 18," Chile coach Claudio Borghi said on Friday night.
"He's an unusual player, sometimes he looks slow, even though he's not, and he's got an ability to see moves that no one else sees. He makes passes that are unique.
"Maybe it's because of that that there's so much admiration for him in a football-crazy country like Brazil."
Borghi will have to decide whether to field Valdivia from the start in Chile's final Group C match against Peru on Tuesday. Matias Fernandez and Luis Jimenez are the other two candidates for the playmaker's role just behind the forwards.
