"We've set ourselves high standards and everyone involved, from the staff, the players and of course the fans are all disappointed," Dier said to the club's official website.
"We've got to this point of the season with four games left and the last chance we had to win a trophy has gone, that's difficult to take.
"We all want to win trophies and to have not won one after these four seasons together is really disappointing.
"That's football and now we have to finish the season strongly and look to the future.
"For the club to get Champions League football again is so important and that's what we're aiming to do by the end of the season.
"We deserve it and we need to show that in the next four games to earn the right to play in the Champions League next season.
"That's the standard and the level the club is at now and where we deserve to be."