The Europeans, who are 33 places higher than the three-time African champions in the latest FIFA rankings, have never played Nigeria at senior level.
Croatia coach Zlatko Dalic indicated last week he was having sleepless nights worrying about the tactical approach to enable the Blazers to get something from their clash against the Eagles.
And Rohr, who also lead his troops against Iceland and South American giants Argentina in the group, has admitted that the Eagles face a tough challenge when they take on the Blazers at Kaliningrad Stadium.
“The first game is always the most difficult,” the 64-year-old German said after the December 1 draw in Moscow.
“It’s the first game and if we start well we can have a chance to go through. Croatia will be the most important game because they have technical quality and play very good football.”
The former Burkina Faso manager, who confirmed on Saturday that Poland had agreed to play Nigeria on March 23, also explained why he decided to accept the White and Reds’ friendly. Poland open their Russia 2018 campaign against Senegal in Moscow on June 19.
“Croatia are capable of great things with a team of stars playing in the biggest clubs,” Rohr told football365.f in an interview.
“They are able difficult to beat the biggest, but also to be surprised by less prestigious teams. It will be up to us to question them. Their technical qualities are huge but we also have a quality team.
“This is the most important match and we hope to prepare for it – against opponents similar to Croatia. So we will play Poland at home on March 23. We are looking for a second opponent in Europe for another FIFA date of the spring.”
The former Gabon coach also says he expects a tough match against debutants Iceland in Volgograd on June 22.
The tiny European nation and Nigeria have met once, with Our Boys cruising to a 3-0 defeat of the Eagles in a friendly affair at Laugardalsvollur, Reykjavík, Iceland, on August 22, 1981. Only 1,113 fans watched the game.
“Iceland have worked hard for 10 or 12 years with extraordinary structures to play football all year long despite the harsh weather conditions,” Rohr said.
“Domes of football, where you can play at any time have been installed, with a dozen per region. Work is done from an early age. They are a team that know how to play football and who are very physical.”
He added, “The match (Iceland versus Nigeria) in Volgograd will be very a difficult game.
“(Croatia) supporters will come in large numbers to cheer on their team. It will be an unprecedented match in the history of the World Cup, which adds spice. In this group, it is amusing to see that the four teams know each other very well. Croatia know Iceland, who were in their qualifying group, well and Nigeria know Argentina very well, since this is the fifth time the two nations will face each other in the finals.”