Arsenal boss Arsene Wenger is saddened by Cesc Fabregas' departure to Barcelona.
Wenger fought tooth and nail to retain the playmaker, but accepts the club finally relented in granting his wish to leave.
"We've lost a world-class player," said Wenger.
"We are sad about it. We did fight to keep him. In the end we've respected the desire of the player.
"The club is 125 years old this season and many big players have left and the club went on.
"That's what we want to show, that we have the strength and unity to fight on."
As he was unveiled at the Nou Camp, Fabregas praised Wenger.
He said: "I'll never have enough words to thank him for all he's done for me.
"I'll never forget him. I don't think he has such a good image here, he has been portrayed as something he's not, in my opinion. If today I am here with you then it's greatly due to him.
"I can't express my admiration for him strongly enough, I owe it to him that I am here."
