Celtic defender Darren O'Dea said the Champions League defeat by AC Milan has hit the players hard.
Darren O'Dea said the players were gutted after losing to Milan
O'Dea starred in the centre of defence alongside Stephen McManus, but was unable to prevent Kaka securing a 1-0 victory with a goal in the 93rd minute.
"It was a desperately disappointing end to our campaign and there was a lot of emotion in our dressing room," said the 20-year-old Irishman.
"We are a very close-knit team and are all proud to have been a part of it."
O'Dea said the players felt they had played well enough over the two legs to go through.
In the end the breaks just didn't go our way but there is a great feeling of pride
"In the end the breaks just didn't go our way but there is a great feeling of pride as well," the defender said.
Celtic had a penalty appeal rejected when Milan captain Paolo Maldini appeared to handle in the box.
But O'Dea said the referee could have been unsighted.
"It was definitely a handball by Maldini and I turned to the referee to appeal.
"However, in fairness he was in a difficult position and looking through a ruck of bodies so it was difficult for him to see it properly."
O'Dea said Celtic were now focusing on Sunday's Old Firm game and wanted to win the game.
Celtic manager Gordon Strachan was full of praise for his players after their extra-time defeat at the San Siro.
"I'm very proud of them," he said. "If there was a Champions League trophy for guts and determination then we must be in with a chance of winning it.
"There were two great teams - one with more technique, one with incredible heart, will and determination.
"If we can improve on technique we'll be a good side. That's the vision - we've got an incredible will to win."
Strachan would not be drawn on Celtic's penalty appeal, saying: "I don't want to sour the night with headlines about referees.
"The night belongs to the players who played the game and supporters of both sides. I'll leave the rest for everyone to get on with."