Barcelona La Masia staff remain frustrated over the club's failure to re-sign Takefuso Kubo.
Kubo had been with Barca since a junior before being forced to return to Japan as part of FIFA sanctions over their youth recruitment policy.
Barca staff had expected Kubo to eventually return, however Real Madrid swooped to land the FC Tokyo whiz last month.
Kubo is already impressing Castilla coaches, convinced they've pulled off a transfer coup.
And a La Masia source told AS: "Kubo? This is the worst mistake of Bara for several years."
