Kyle Lafferty feels Northern Ireland let their fans down against Poland, but has promised a response when they take on Ukraine on Thursday.
In their first match at a European Championship on Sunday, Michael O'Neill's men lost 1-0 in Nice to an Arkadiusz Milik goal.
And, ahead of their crucial second Euro 2016 fixture against Ukraine, Lafferty knows there must be a marked improvement if Northern Ireland are to have any hope of qualifying from Group C.
"For Michael, for his coaching staff, for all the people who've paid good money to come out here, we let them down and we'll put it right on Thursday," the Norwich City forward said.
"A win could take us out of this group. We still have belief. We've got two games to put it right and I'm sure we'll give a better performance than we did against Poland."
"We'll look into it, get our heads sorted, get our tactics right and I know we'll put up a far better performance than this.
"Not one player will let the fans down. Even if we don't get the result we want on Thursday, the fight and determination that got us here will be there.
"[Against Poland] We were a shadow of the team that got us here. It's okay talking about nerves, but the fight and the determination were not there either.
"We just got hit by a very good Poland side and we didn't know what to do.
"Whenever we've faced teams like that before, we could take control of it, take the game by the scruff of the neck and create chances, but we didn't do that against Poland.
"We pretty much froze on the spot."
Ukraine also lost their first game of the tournament, 2-0 to Germany.