Arsenal manager Arsene Wenger had expressed his sadness after Cesc Fabregas sealed his return to Barcelona on Monday.
The Gunners initially signed the Spain international as a teenager and helped to mould him into one of the world's best midfielders.
After years of speculation linked him with a return to Camp Nou, the 24-year-old has signed a five-year deal with the Spanish champions.
Wenger fought tooth and nail to retain the playmaker, but accepts the club finally relented in granting the player his wish to leave.
The Frenchman is sad to see Fabregas go although big names have left in the past and he insists Arsenal will continue to thrive.
"We've lost a world-class player," commented 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."