Giovanni Trapattoni has hinted that he could ditch his tried an tested 4-4-2 to accommodate for another midfielder but has also suggested that he feels Robbie Keane can play in the free role behind a lone striker so a change in personnel is unlikely.
Kevin Doyle is likely to start up front ahead of Long and Walters despite being in and out of the side at Wolves last season.
Ireland fans will be keen to see James McClean tested on the big stage but may have to rely on cameo appearances from the bench to see the young winger, while Andrews and Whelan should keep Gibson out of the midfield.
Slaven Bilic's reign as Croatia manager will end after the tournament and he has a couple of tough decisions to make in his line-up, with centre-back Dejan Lovren withdrawn from the squad through injury along with Ivica Olic.
Up front he must choose between Eduardo and Nikica Jelavic, with Mario Mandzukic likely to take the role as support striker.
Dujmovic and Vukojevic vie for the starting defensive midfielder spot, while the Croat's lack real width with Kranjcar and Rakitic potentially playing on the wings.
Ireland will play as usual and look to build from a potential clean sheet. However, they must try to open Croatia up at some stage, knowing that an unlikely progression from Group C may hinge on a win in this one and attempting to pick up a draw with Spain or Italy.
Croatia will need their creative players to be on top form to break down a resolute and well-drilled Ireland defence, so Luka Modric could be the key to this game. If Ireland can shackle the Spurs man they may have a real chance.
Both sides will see this as a must win game but Croatia are more likely to look to control possession and though a draw doesn't really help either side, it could be the most likely outcome.
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