However, after 13 appearances for the Gunners, he decided another move was necessary to push his claim for a place in the France squad at Euro 2008 and secured a transfer to Portsmouth, where he would go on to win the FA Cup final at Wembley.
Wenger, though, is in no doubt had the young midfielder shown more "patience", the opportunities would have come his way with the Gunners, especially following the departure of Mathieu Flamini to AC Milan.
"I came to the conclusion that Diarra could not cope with the fact that he was behind the other players here in midfield," said the Gunners boss. "I thought the best option was to let him go because I already had Denilson, [Abou] Diaby and Gilberto all trying to get into the team as well. It was a congestion."
Wenger told the June edition of the official Arsenal magazine: "I bought Diarra in the summer because I thought Flamini might leave at the end of the season and if he was able to be patient, he would get his chance. "It turned out he wasn't capable of that. With Euro 2008 in mind, he panicked.
"I did explain when he joined that he might have to be patient, and he acknowledged it, but he couldn't cope with the situation, and also did not want to go on loan anywhere either."
Just what shape Arsenal will be in for the start of next season remains to be seen. With Flamini already gone, speculation continues that winger Alexander Hleb will soon follow him out of Emirates Stadium, with Real Madrid and Inter said to be leading the chase.
Meanwhile, reports in Italy claim Roma are ready to move for veteran Brazilian Gilberto, who saw his impact limited last season and is entering the final 12 months of his existing deal.