Arsenal boss Arsene Wenger admits selling Alex Song to Barcelona was a gamble.
Diaby, plagued by injuries during his time at Arsenal, limped off after just 18 minutes of Saturday's 2-1 defeat to Chelsea.
Wenger said: "It was a gamble but I was calculating that Jack Wilshere was coming back.
"We'll see if it was a good decision at the end of the season."