The Springboks suffered a second successive defeat in the tournament when they lost 40-7 to New Zealand in Wellington today.
Although they could still mathematically win the tournament, de Villiers has suggested that his side will now move their focus to the World Cup in September.
"Pretty much the Tri-Nations are gone for us," said de Villiers. "We'll move our focus to preparing for the World Cup.
"The All Blacks are more ready [than South Africa] now for the World Cup and they deserve the tag of favourites to win it."
South Africa are missing 21 first-choice players for the Tri-Nations tournament through injury, although media rumours suggest that they are taking part in a secret World Cup training camp.