Middlesbrough boss Gareth Southgate believes his club will "stand strong and fight back" after being relegated on the final day of the season.Boro needed to beat West Ham to have a hope of staying up, but lost 2-1 to end their 11-year stint in the top-flight.
"It's a low for our club, our players, our staff and our supporters," he said.
"We grieve tonight but the future starts tomorrow. We are going into a very competitive division but we want to take that challenge on."
Boro were relying on a sequence of results involving Hull and Newcastle losing - which they did - but the first priority was victory at Upton Park.
Gary O'Neil gave Boro a boost when he cancelled out Carlton Cole's first-half strike for the Hammers, but 19-year-old Junior Stanislas poked home on the hour to seal the visitors' fate.
With Hull finishing above Newcastle and Middlesbrough despite a 1-0 loss to Manchester United, Southgate said it was "incredible" that 35 points had been enough to avoid the drop.
Since the turn of the year, Boro slowly slid down the table, finishing the season with just seven wins after scoring only 28 goals.
"You look back at October and November and we were going well, but then certain things happened," Southgate added.
"Our youngsters have shown great effort and endeavour throughout the season but during the last few games we just ran out of players."
Southgate was without England winger Stewart Downing, skipper Emanuel Pogatetz and record signing Afonso Alves for the defeat at the Hammers - their 15th away loss in the whole of the season.
However, the 38-year-old Boro boss, who took over the reins at the Riverside from Steve McClaren in 2006, remained resolute and optimistic.
"It's a harsh lesson for us all," the former England defender said. "We now stand strong as a football club and fight back.
"It's a painful blow but we have to take the pain and move forward."
Midfielder O'Neil admitted the players were very down and that their relegation had been sealed long before the season's final match.
Considering fine wins over Liverpool in February and at Aston Villa in November, he said: "We've had some good results but we just haven't been able to cross the line.
"The lads are very disappointed but looking to bounce back. We had too small a squad and we've picked up too many injuries."