Jens Lehman admits he is surprised Arsenal spent £35million to sign Shkodran Mustafi from Valencia.
The Gunners turned to Mustafi to ease their defensive injury crisis, with Per Mertesacker and Gabriel Paulista injured.
And former Arsenal goalkeeper Lehman says he did not expect Arsene Wenger to sanction such an expensive deal for the Germany international.
“It’s unlike Arsenal to sign a defender for almost €40m – I’m surprised,” Lehman said.
“I think he’s probably the most successful manager in making money for the club.
“He’s always taken part in the Champions League, buying cheap and selling expensive.
“He was a major player in setting up the new stadium and at the same time always playing Champions League football.”