"We have to make sure we play together as a team which is the most important thing; no individual players," Obi told a media conference on Friday.
"No need to think that we are favourites, we're still underdogs, so we have to go as underdogs in this World Cup and hopefully we can get good results," he said.
Nigeria, known as the Super Eagles, are ranked 47th by FIFA and face Argentina, ranked fifth, Croatia (18) and Iceland (22) in Group D.
"We have a very tough group," said Nigeria's coach, Gernot Rohr. "It will be a surprise to come out of this group for a lot of people but perhaps not for me because I believe in my team and I think that my team, even though it's young, has enough experience."
Obi added: "We want to do well, we want to do better than ever, we want to go one step further."
(Writing by Paul Carsten; Editing by Clare Fallon)
