Twelve teams are to be narrowed down to three eventual qualifiers, via a trio of separate qualifying paths.
Euro 2016 champions Portugal were pipped to top spot in Group A after losing to Serbia on the final matchday and Cristiano Ronaldo, Bruno Fernandes and Diogo Dalot now know who they will have to beat to make it to Qatar next winter.
Fernando Santos's side are seeded and will play Turkey at home in the semi-final, with four-time world champions Italy or North Macedonia - who have never appeared at the World Cup finals - then waiting in the Path C final should they be successful.