South Africa goes in as the underdog against titleholder Australia in the World Test Championship final at Lord's from Wednesday.

South Africa are quietly confident of an upset victory in the World Test Championship final with coach Shukri Conrad warning defending champions Australia not to underestimate his inexperienced batting line-up.

Former Test captain Smith, however, also expects conditions at Lord’s to favour spin bowling later in the game, which could work to the advantage of Australia off-break bowler Nathan Lyon.