Wasps director of rugby McGeechan was unveiled as the head coach for a fourth time in London yesterday.
And De Villiers even described the appointment of the 61-year-old Scot, who masterminded a famous series victory over the Springboks in 1997, as "a setback" to South Africa's hopes for next year's three Tests.
"McGeechan's appointment makes them very dangerous," De Villiers told Die Burger.
"He has enjoyed success in South Africa, as player and as coach. He knows the conditions. I am not surprised at all."
Meanwhile, De Villiers also said he was not going to be fooled by stories Wales would be sending a weakened team to play South Africa in two Test matches next month.
Describing the Welsh as "an extremely strong team", De Villiers said they were "basically the team that won the Six Nations".
He added: "Nearly all these players were involved in their Six Nations campaign. Their other scrum-half, Gareth Cooper, has played in 35 Test matches."