With Ricardo Quaresma and towering striker Eder both left on the bench, Portugal coach Fernando Santos deployed playmaker Joao Moutinho behind the front two and in front of a three-man midfield marshalled by Danilo.
Iceland, who are playing in their first major tournament, opted for a familiar 4-4-2 with Kolbeinn Sigthorsson and Jon Dadi Bodvarsson up front.
Their gameplan will largely rest on the ability of versatile central midfielders Gylfi Sigurdsson and Aron Gunnarsson to hold their own against crafty opposition, while also being expected to feed wingers Birkir Bjarnason and Johann Gudmundsson.
(Writing by Zoran Milosavljevic; Editing by Toby Davis)
