Croatia will top Group D if they can get the best of Spain in their final match of the group stage at the Nouveau Stade de Bordeaux on Tuesday night.
This will be the sixth meeting between the two sides, with Spain winning three of their previous encounters, while Croatia have won just once.
Croatia squandered an opportunity to wrap up their qualification to the next round after giving away a 2-0 lead to draw 2-2 with Czech Republic at Stade Geoffroy-Guichard last week.
A win for Ante Cacic's men will see them finish as group winners, while a draw would still be enough to guarantee second place and a place in the round of 16.
Spain, meanwhile, will be looking to extend their unbeaten run to 15 games at the Euros and continue their miraculous run that has seen them not conceded a goal in 690 minutes of action.
Midfielder Cesc Fabregas insists they will not take things easy against their opponents, as they look to consolidate their spot at the top of the group.
"We have been playing very well, with a certain freedom and fluency. We have been defending very well and that allows us to be fresher going forward," he said at a news conference.
"This next game is very important, even more than people can imagine. It's crucial for us to be first in the group. It will be determinant for the rest of the tournament."
In team news, Luka Modric is going to miss this game with the groin injury he picked up against the Czechs, while no injuries or suspensions have been reported by Spain.