Most Croatian players have improved individually since Euro 2012 but only the June 12-July 13 World Cup will show whether the team can match the sum of its parts, playmaker Luka Modric said.
The Croatians take on hosts Brazil in Sao Paulo in the tournament's opener on Thursday and Modric assessed there was a thin line between success and failure in the 32-nation event.
"We could go far if we get past the group stage," the midfielder told reporters in Croatia's Praia do Forte base on Tuesday.
"I can see very clearly that many of us have improved massively as individuals since Euro 2012 but it is yet to be seen whether we have progressed as a team.
"It's been a while since we played a match as big as this one, we know the Brazilians respect us and we are also aware how fired up they will be to make a winning start on home soil.
"They are a phenomenal team with Marcelo, Thiago Silva and Neymar the three outstanding players in my opinion.
"Hence we have to breathe as one on the pitch because none of us can put up a one-man show against a team of such fortitude. It will be a titanic tussle in midfield and we are doomed if we surrender possession and sit back."
The Croatians, who stunned the world when they reached the 1998 tournament semis in their first World Cup as an independent nation, have since flattered to deceive.
They failed to progress beyond the group stage in any of their three following World Cup appearances and also fell short in Euro 2012, finishing behind eventual winners Spain and runners-up Italy in a tough preliminary pool.
Brazilian-born striker Eduardo da Silva said Croatia's fate in the tournament could be heavily influenced by their performance against the host nation.
"Brazil are the tournament favourites so beating them will be a big ask but how well we hold our own could determine our achievement in the group stage of the competition.
"On the other hand, it will be very difficult for them to come back if we score first. My family will be here and I am not sure who they will support but the most important thing is that we play well to keep a good atmosphere in the dressing room."