The Manchester United winger was lucky the injury, which occurred during Ecuador's 0-0 draw with Paraguay at the Colon stadium in Santa Fe on Sunday was not more serious, Tony Ocampo told Reuters.
"[His opponent] stepped on his foot and very nearly fractured it again," Ocampo said, referring to the same left ankle Valencia dislocated and broke in September playing in the Champions League.
"He has a bruise on the spot where he has a titanium plate, he couldn't put his weight on his foot, but the swelling has gone down about 40 percent since Sunday. He won't make it to Saturday but he'll be there for Brazil."
Ecuador face Brazil in Cordoba on July 13 in their final group match. Sunday's opening Group B matches between Brazil and Venezuela and Paraguay and Ecuador ended goalless.
Paraguay midfielder Edgar Barreto, also hurt in Sunday's match in Santa Fe, will miss their clash with Brazil in Cordoba on Saturday also with a foot injury, coach Gerardo Martino said.
"We thought that with a week's rest he'd be able to carry on but it seems [the injury] is a little more complicated," Martino told a news conference, adding Victor Caceres could stand in for Barreto in the team.
Barreto injured a metatarsal in his left foot, the same problem for which he had surgery before last year's World Cup finals.
Caceres is recovering from a knock during a warm-up friendly against Chile in Asuncion 11 days ago but should be fit to start.
