Fulham caretaker manager Scott Parker said he was “devastated for the club and the fans” after their relegation from the Premier League was confirmed by a 4-1 loss at Watford.
His side needed to avoid defeat to keep their faint hopes of survival alive.
It was 1-1 at half-time but they conceded three times after the break.
“We always knew it was a tough ask,” said Parker. “But that five or 10-minute spell from 2-1 onwards was our season in a snapshot.”
He added: “The way we lost the game was most disappointing for me.”
Ryan Babel had equalised after Abdoulaye Doucoure’s stunning opener for Watford but second-half goals from Will Hughes, Troy Deeney and Kiko Femenia made it nine league defeats in a row for Fulham.
They were promoted to the Premier League after an impressive Championship campaign and were tipped by many to do well.
However, after spending more than £100m last summer, their season has been a huge disappointment, with managers Slavisa Jokanovic and Claudio Ranieri both sacked.
Caretaker boss Parker has lost all five of his games in charge with Fulham relegated with five league games still to play.
“I am obviously bitterly disappointed,” Parker said. “I have ideas [of where it went wrong] but it’s not the time to broadcast them.
“When a club gets relegated from the Premier League, you know there are some serious issues.”
In a statement, Fulham chairman Shahid Khan apologised and assured fans of his “total commitment” to the club.
“Our results over the past three months were as troubling for me and everyone associated with our club as I know they were for you,” he said.
“Last night’s outcome made official what we didn’t think would be possible in August and tried desperately to remedy and avoid as the season wore on. For me, that makes today the most difficult day of all.
“I am sorry that we let you down. Our goal this season was to build on what we achieved in promotion and deliver on our pledge to invest heavily in the squad, ensuring that Fulham would always compete in the Premier League and, no matter the result, never disappoint.
“That didn’t occur and, for that, we hold ourselves accountable. We will reflect, plan thoroughly and respond accordingly.”
Ex-Fulham midfielder Steve Sidwell on BBC Radio 5 Live
They were one of the best footballing teams in the Championship but this year, defensively, it’s been a shambles.
Signing 12 players would have been demoralising for the existing players. The squad needed strengthening but not to that extent.
They did not name a consecutive back four in the first 10 games and as a result they have been all over the place.
The players who got them into the Premier League deserved a crack at it but they did not get the chance.
They need to give the job to Scott Parker because he knows the core values of the club, he understands the Championship and the fans want him to get it.
Fulham arrived in the Premier League through the play-offs after scoring 79 goals and losing just eight games.
With a talented squad built around captain Tom Cairney and teenager Ryan Sessegnon, they were expected to make an impact in the Premier League.
They showed great ambition, spending a record sum for a newly promoted side to bring in 12 players, but this fundamentally changed the team that had performed so well together.
Nearly £50m was spent on Jean Michael Seri and Andre Frank Zambo-Anguissa who between them have contributed a mere one goal and two assists.
At the back, their goal difference of +33 in the Championship has become -46 in the Premier League and their leaky defence has conceded 76 times, 17 more than fellow strugglers Burnley, Cardiff and Huddersfield.
Away from home, they remain the only side in the top four divisions of English football without a win, achieving a miserable two points from 17 games.
Centre-back Tim Ream hinted at a lack of leadership in the Fulham dressing room when he talked about “home truths” in the Fulham dressing room after the game.
“There should have been strong words all season long,” he said. “We’ll see if the home truths resonate with some of the guys, and if they don’t, that’s on them.
“We haven’t shown a togetherness, unity, desire or passion. We need to find it from somewhere.”
The lack of stability on the pitch has been mirrored on the sidelines where first Jokanovic and then replacement Claudio Ranieri were sacked for failing to turn ambition into reality.
It has been left to Parker, who played more than 100 times for Fulham, to pick up the pieces.
@sharmander961: I was at Wembley in May when the day ended in tears. I was at Watford and the day is ending in tears. Wherever Fulham go, I’m dragging my crying self with them!
@KatieShanahan3: Genuinely really gutted Fulham have been relegated. There was so much excitement at the start of the season, new press room, new facilities, new faces. Just such a shame that the £100m in the summer couldn’t keep them up.
@mathew_halford: Being relegated goes far beyond the players. This is a recruitment policy that was doomed from the very beginning, overseen by the owners.
@JoeShennan: The sheer scale of mismanagement at Fulham this season is almost difficult to believe. Extraordinary how a superb footballing side with identity and character can go to the utter shambles of this year. Big questions need to be asked of those at the top of the club.
@AmberDFWgirl: So sad Fulham have been relegated from the Premier League to the Championship. I love Craven Cottage, a beautiful place to watch a football match & great supporters.