They have made it through to seven out of nine World Cups and European Championships as an independent nation but a 0-0 draw in the first leg in Reykjavik has left the tie in the balance.
Having missed the 2010 tournament in South Africa, failure to reach next year's event in Brazil would spell disaster for success-hungry fans who expect more from a talented generation of players led by Real Madrid playmaker Luka Modric.
Coach Igor Stimac made way for novice Niko Kovac after Croatia picked up only one point in their last four Group A matches.
Having scraped into the playoffs, they could only muster a tepid performance against Iceland, who were reduced to 10 men early in the second half, with few signs of improvement.
"It's difficult to turn things around overnight but I believe we are on the right track, although we failed to score against a side inferior in every department in terms of quality," veteran defender Josip Simunic told reporters on Sunday.
"This is a crucial match for this generation and we have to be more intelligent in the return leg as well as prepared for any situation," he said.
Modric conceded he was well below-par and agreed that his international form was a far cry from club performances this year.
"I am going through a rough patch with Croatia and the whole team is suffering, but I can't really explain why," he said.
"I have faced up to this cold truth and I keep looking for ways to restore my composure but now is not the time for in-depth analysis why we are underperforming.
"We have to show now that we are tough enough to overcome adversity and put our bodies on the line if we have to. Me first."
Having punched above their weight to reach their first playoff, Iceland are likely to stick with their trademark industrious approach and hope for a smash-and-grab away goal that could unsettle their more resourceful opponents.
They are likely to be without first-choice striker Kolbeinn Sigthorsson, who faces a race against time to shake off an ankle injury sustained in the first leg, when he was stretchered off just before halftime.
Olafur Skulason, sent off in the 50th minute for a professional foul, is suspended, meaning Iceland's Swedish coach Lars Lagerback is likely to throw veteran striker Eidur Gudjohnsen and the versatile Eggert Jonsson into the fray.
"We still don't know if Sigthorsson will be fit, there is a swelling and a sprain so it's a race against the clock," said Lagerback.
"I said before the first leg that we could stand our ground against Croatia and eliminate them. I stand by that remark, we have it in us to qualify for the World Cup and that will be our mission in Zagreb."
- Sports & Recreation