The Super Eagles drew their final match 2-2 against South Korea, not enough to salvage two opening losses to Argentina (1-0) and Greece (2-1).
In an entertaining clash, Nigeria scored through Kalu Uche (12) and a Yakubu Ayegbeni penalty (69), with South Korea responding through Lee Jung-Soo
and Park Chu-Young either side of half-time.
“I have responsibility for the results,” said Lagerbäck, who guided his home nation Sweden to the second round of the World Cups in 2002 and 2006, but has only been in charge of Nigeria for five months.
“I’m the one doing the gameplan and the one training the team. Maybe with a little more time it could have been a little different.
“I have felt privileged to be the coach of Nigeria. It’s been a fantastic journey in many ways.”
“As for the future, I don’t know, the focus has been on the World Cup,” he said, adding that there would be a full post-mortem on Nigeria’s performance before any decision would be taken on whether he stay on or not.
Lagerbäck added: “I’m disappointed. It’s very disappointing for the Nigeria team.”
“I’ve been really impressed by the players’ professionalism. But results speak for themselves and we didn’t qualify for the second round.”
“We started (the game against South Korea) really well, but we made a little mistake and it was 1-1.”
“We played rather well and had chances to win but we didn’t find that last goal.”
Lagerbäck also said he thought his team had defended “mostly well” at the set-piece despite conceding the first goal from a corner and the second a direct free-kick.
“Goals from set-pieces happen. It’s about 25 to 30 percent of all goals come from that,” he said, also defending the choice of the coastal city of Richards Bay as the team’s training camp as opposed to a high-altitude one.
Training at altitude, he argued, “has a marginal effect and we took the decision because of other advantages to staying in the Richards Bay area”.
Nigeria captain Nwankwo Kanu, whose appearance against South Korea was his first after missing out on selection for the first two games, added: “We’re not happy. One more goal and we could have qualified.”
“But we’ll take the positives. We played well but we as everyone knows, if you don’t score goals you don’t win matches.”