The Juventus midfielder underwent knee surgery on May 7, putting his World Cup campaign in doubt after a strong season with the Serie A champions.
Sampaoli will wait until the FIFA deadline on June 2 to finalise his 23-man squad to face Spain, the Netherlands and Australia in Group B.
Vidal, 27, is expected to be training again next week, according to Sampaoli.
"Today is an unknown," Sampaoli told a news conference on Thursday, a day before Chile face Egypt in an international friendly.
"Progress is favourable, but not yet in the field. Next week he should be back on the pitch."
Vidal's absence would be a blow for Chile, who have already lost key midfielder Matias Fernandez due to an ankle injury.
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