Arsenal boss Arsene Wenger says Alex Song pushed for a move to Barcelona.
The two clubs confirmed the transfer yesterday.
Speaking after Saturday's goalless draw against Sunderland, Wenger said: "He expressed a desire to go to Barcelona.
"It is frustrating, we have learnt to deal with that. I believe as well that the financial potential of some clubs is massive and that makes a difference."
Wenger, however, feels Arsenal have enough cover in midfield.
"We have [Jack] Wilshere coming back, I believe in one and a half months. We have [Abou] Diaby back, we have [Tomas] Rosicky not far away and we might bring another midfielder in as well.
"You have to be patient a little bit [over any new signings]."