Giroud's second season with the Gunners has got off to a superb start, with the Frenchman finding the net six times in 12 matches, including the first goal in four successive Premier League games.
Wenger told The Guardian: "I always thought that his second season would be the decisive one. I was not too worried when we didn't bring anyone in because I thought he had a good chance to develop.
"Giroud is amazing because he develops well. If you compare his technical level when he arrived to how he is today, he has highly improved.
"Now he enjoys combining much more. From a player who was just thinking 'I have to score', he has now become real team player."