Liverpool hero Didi Hamann believes Arsenal have never recovered from the sale of Alex Song.
Song spent six years at Arsenal after an initial loan spell from French club Bastia before joining Barcelona in 2012 for £15million.
Hamann told PaddyPower: "Since Alex Song left the club, Arsenal haven't addressed the fact that they lack a proper defensive midfielder.
"They've got Francis Coquelin and Mohamed Elneny who are OK players – but OK isn't good enough for Arsenal.
"[Granit] Xhaka could have been the man to do it, but it hasn't turned out that way."