Diaby is out for at least three weeks after pulling a thigh muscle against Chelsea.
"Diaby’s injury record is not good," said Wenger. "I was concerned about him of course. It was a gamble, but I was calculating as well that Wilshere was coming back, Francis Coquelin is here but was sick and Emmanuel Frimpong is back.
"Tomas Rosicky is coming back so we have many midfield players. We don’t have many physical players but Mikel Arteta has shown he can be a great defensive midfield player.
"He was outstanding in that area against Chelsea. We’ll see overall if it was a good or bad decision at the end of the season."