Holders Spain and Croatia look to book their places in the Euro 2016 knock-out stages on Friday, with Spain also aiming for a better overall showing.
La Roja laboured to a late 1-0 over the Czech Republic from Gerard Pique in their Group D opener, dominating play but not fully convincing.
The Croatians join them on three points from a 1-0 against Turkey thanks to Luka Modric's excellent first-half volley, but were wasteful after the break as they had several further chances.
Spain now play Turkey and Croatia the Czechs, and if both win they are safe into the last 16 before their meeting which would then be for the group victory.
Spain coach Vicente del Bosque may bench midfielder Cesc Fabregas after an unconvincing game and replace with Bayern Munich's Thiago who says he is ready for the task.
"I want to play as many minutes as possible, we all do," Thiago said. "The competition for places in the squad is massive, because all of the players are of very high quality."
Turkey coach Fatih Terim will meanwhile hope for better showings of his stars Arda Turan of Barcelona and Bayer Leverkusen's Hakan Calhanoglu.
He could also consider starting with teenage sensation Emre Mor who came on late against the Croatians but was unable to create a turnaround for his badly tiring team.
"The lesson is not to lose the ball in an easy way and to run and fight harder," Terim said, looking at the Spain game, adding defiantly "it is not over until its over."
Like the Turks, the Czechs face elimination if they lose a second time, in St Etienne against a Croatia team considered contenders, given their class with the likes of Modric, Ivan Rakitic and Mario Mandzukic.
Croatia expect to have captain Darijo Srna available after the 34-year-old left the team camp during the week to attend his father's funeral.
The 2012 runners-up Italy will meanwhile also advance, from Group E, if they follow up on their impressive 2-0 over Belgium with a second win, in Toulouse over Zlatan Ibrahimovic's Sweden who were held 1-1 by Ireland.