Roberto Martinez said he never expected Wigan to be relegated from the English Premier League, but vowed to jump straight back up, after a 4-1 loss to Arsenal at the Emirates consigned them to at least a season in the Championship.
Wigan made a real fist of the game for 60 minutes, with Shaun Maloney cancelling out Lukas Podolski's early goal.
However, some shambolic defending, the theme of Reading's entire season, again came back to haunt them as Arsenal exploded in an eight-minute spell to score three goals in the space of eight minutes, via Theo Walcott, Podolski and Aaron Ramsey.
Wigan needed a win to have any realistic chance of staying up in the Premier League, and Martinez insisted his side would definitely return to the top flight sooner rather than later.
"I never expected this to happen," Martinez told Sky Sports. "We have an incredible bunch of players at the club, they don't deserve this.
"It is a tough day for the football club. We have had an incredible eight years in the Premier League. We have to take the good things and make sure we build for the future.
"The relegation is really disappointing but it is something that we can rectify. We will bounce back as we always do as we always do at Wigan Athletic.
"The club is on a fantastic financial footing, we are stronger than ever in that respect, our football style and philosophy is something for the long term.
"I am glad that this group of players were able to show what they were capable of -- to win the F.A. Cup is an incredible achievement.
"To win the F.A. Cup is an achievement that will live forever for the football club and for every individual and especially for the fans."
Defending is what cost Wigan their place in the Premier League, and Martinez acknowledged the problem, although he was not helped by a series of injuries to his defenders throughout the season.
"We conceded far too many goals," Martinez added. "Going forward we have been magnificent, but the amount of injuries that we have had in the backline is something I have never seen before.
"When you have four, five or six players missing from that position, when you keep making changes in the backline, the partnerships suffer and you concede so many goals it costs you points without playing badly."
Martinez, though, said Wigan could be proud of their achievement - staying eight years in the Premier League, when no-one had given them a prayer when they were first promoted way back in 2005.
"Nobody gave us a chance of having more than one season in the Premier League so there are many aspects for them (the fans) to be extremely proud of," Martinez said.
"We have to make sure that we get stronger and that the future of this football club is very bright.
"It's a time for everyone involved with this football club to very proud of the last eight seasons in the Premier League and of winning the F.A. Cup.
"As a football club we have been defying the odds year-after-year and this season we have been playing outstanding football week-after-week.
"It's time to have a breather at the end of the season and make sure that we have all the good things together at the club."