Progression through to the Round of 16 for Croatia has been seamless. They were comfortable winners against Nigeria in their opening game and then dispatched a hapless Argentina side with ease on Thursday night.
For Iceland, things have been more difficult. The minnows - who, you will now have been told by every commentator and pundit at the World Cup, have a population of a little over 300,000 - earned a commendable draw against Argentina in their opener. That, it seemed, put them in a strong position, but they were beaten 2-0 by Nigeria in their following game.
A win for Heimir Hallgrímsson's side against Croatia, then, is essential. Even then, they will rely on Argentina getting a result in their meeting with Nigeria.
Croatia go into this game knowing that a point will guarantee top spot in Group D. They have impressed so far: midfielders Ivan Rakitic and Luka Modric have earned widespread plaudits, and they are yet to concede a goal.
Iceland might be encouraged, though, by memories of qualification. They finished above Croatia, who needed to secure their place in the finals with a playoff.
Here are three key battles that could decide Tuesday's encounter: