But Wenger believes that the 23-year-old Diaby, who signed from French side Auxerre in January 2006 but has been restricted to 64 league appearances by a series of injuries, could now be ready to step up to the task.
"He worked very hard in the summer and this could be his season," said Wenger.
"He has prepared very well, looks sharp and strong and has everything for a Premier League midfielder."
Arsenal look likely to miss the leadership of captain Cesc Fabregas in the second leg of their Champions League qualifying tie against Celtic.
The Spaniard limped out at half-time of their win over Pompey with a hamstring problem.
"If it's a little pull he will be out for three weeks, if it's tightness he could make Wednesday. We will see in the next 48 hours," said Wenger.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.