Iniesta suffered a thigh injury during a 6-0 friendly win over Poland and has been training away from his team-mates in a bid to recover in time. And Del Bosque believes the Barcelona midfielder is winning his race to be ready for their Group H opener in three days' time.
European Champions Spain are one of the favourites in South Africa, and Del Bosque admits he is altering his opinion of who their main rivals will be as the tournament progresses.
He added: "The game between England and the United States disappointed me. They were my great favourites. I think Argentina are a really strong candidate if (Lionel) Messi continues playing at his level."