Vilas was destined to arrive late for the first ball at 10. 30 a.m. (0830 GMT) because Cricket South Africa could not book him on a flight earlier than 8 a.m. from Port Elizabeth, where he was due to play in a four-day provincial match.
Flights from the coastal city to Johannesburg take two hours and the usual heavy traffic from the airport to the stadium looks set to add the drama of the dash.
New captain AB de Villiers will keep wicket from the start of the match if South Africa field, Cricket South Africa said.
De Kock sustained a freak injury to his right knee on Wednesday.
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"Quinton slipped and sprained his right knee at home late yesterday afternoon," South Africa manager Mohammed Moosajee said on Thursday.
"Initially he didn’t think it was too serious but woke up after midnight in pain and with a swollen knee. He will have investigations done later today to ascertain the extent of the injury."
The 30-year-old Vilas is coming off a career-best 216 not out in last week's round of provincial matches. He played four tests for South Africa in India in November but was dropped after the series.
(Reporting by Mark Gleeson; Editing by Nick Mulvenney)
