Middlesbrough captain Ben Gibson said Monday's 3-0 loss to Chelsea was "the lowest point of my life" as their relegation from the Premier League was confirmed with two games to play.
After just one season in the top flight, Boro will return to the Championship, where they spent the previous seven campaigns. The club matched a record with their fourth relegation from the Premier League.
Goals from Diego Costa, Marcos Alonso and Nemanja Matic -- all through the legs of Boro keeper Brad Guzan -- sealed their fate, but Gibson said his club had been second-best for a long time.
"It's not just tonight, it's a full season," he told Sky Sports. "From top to bottom we haven't been good enough. Players, staff, myself. They were much better in every department. It could have been 4,5,6-0.
"It was the lowest point of my career. We've got to put it right. In fact it's the lowest point of my life, not just my career. It means that much."
Gibson, who joined Boro's academy as a 12-year-old, also said the club's fans deserved better.
"The fans didn't stop singing, wherever we've been this season they've been the same," he said. "The fans deserve Premier League football and we have to find a team to do that. We have to reflect on what's gone wrong."
On their immediate return to the second tier, Gibson told the BBC: "After the highs of last season, to be honest we've wasted an opportunity to play in the best league in the world."
Middlesbrough boss Steve Agnew, who replaced Aitor Karanka in March, said the dressing room was quiet after the defeat.
"I'm frustrated and disappointed," he said. "We've just come away from a silent dressing.
"We were reasonably well organised, but at the same time we didn't get a foothold in the game for long enough. Chelsea have top players and are a top team, very much on the front foot to push us back. At half-time, conceding two goals the way we did was disappointing. From a defensive point of view we gave ourselves a mountain to climb.
"We've had 36 games and we have two to go and it's been a really tough season. That's a disappointment, it wasn't just this evening, it's been ongoing for as long as the season has been with us. We haven't scored enough goals and ultimately you have to score goals to win football matches."
And he was tight-lipped about his future with the club, saying: "I think the most important thing in a moment like this is the football club and it's a terrific football club, that's what it's about.
"It's not about my situation, it's about how we reflect over the summer. Finish the season strong, firstly, and then reflect and make sure that Middlesbrough Football Club can bounce back to the Premier League very, very quickly."