George Friend vowed that Boro will come back stronger after suffering relegation from the Premier League.
The defender reiterated praise for the fantastic Boro following after Monday's 3-0 defeat at Chelsea.
"The fans been amazing all season, filling out the Riverside and our allocations away from home, and they deserved better," he said.
"They've stuck by us after some bad results and some bad times.
"We've never really got going properly this season.
"I want to apologise to the fans and thank them, and tell them if they stick by us again we'll bounce back."
Friend says Boro's focus now becomes returning to the top flight at the first attempt.
"It's time for Middlesbrough to reflect on the season and what's going to happen now," he said.
"You have to look to next season, and look positively.
"We've got some good foundations now and compared to where we were six or seven years ago, we're in a strong position going into the league below.
"It feels similar to the Play-Off final - we weren't good enough on that day and we weren't good enough this season.
"But we'll learn from this and come back better.
"It's a step backwards but hopefully we'll take two steps forward next."