Former Arsenal star Martin Keown believes that of Arsenal's departures in recent years, Alex Song is one who has hurt the most.
He is on loan from Barcelona, where his move from Arsenal did not work out well, but now he is getting his career back on track.
Keown told the Mail: "The grass is not always greener. When Fabregas and Robin van Persie left, Wenger let them go to further their careers.
"With Song, it was more of a disappointment. Arsenal invested a lot of time in him and hoped he would want to stay and repay them."
Van Persie and Fabregas were established stars by time they left Arsenal, but with Song - he was part of their side, but did not seem like an essential one at the time, and they way he failed at Barcelona showed him to be lacking the world class status to which he perhaps aspired.
It could be that fact that Song, being not quite an elite player, wanted to quit the club, that irked Arsene Wenger so much.
Looking at the present Arsenal side, he is a player they could sorely do with, as his combative style is proving so valuable in the Premier League. Arsenal have amazingly never really replaced him, unless you count a move to bring back Mathieu Flamini on a free transfer.