The France midfielder is in his ninth year at Arsenal, but he is yet to start 100 league games for the club and missed all-but 16 minutes of last season with a cruciate ligament injury.
Diaby, who thought about retirement, has been able to play a full part in pre-season and featured in Saturday's friendly against New York Red Bulls.
And he said: "My love of football is just so big that I couldn't quit.
"I am still young and now that I have an oppportunity to play again I want to take it. I try to be positive all the time and that has helped me to come back.
"It is great just to be playing again. Now I just hope I can keep like this and continue. My knee is feeling good. I have been working hard on my fitness and strength.
"I am really confident I will be able to stay injury-free. I have worked hard for over a year."
Diaby also played 45 minutes of Arsenal's pre-season opener at Boreham Wood, and after that game Arsene Wegner said: "You wish that he just gets through the game, which happened here - I’m very pleased with that.
"If you get a fit Diaby back, it will be a major asset for our team. At the moment we go step-by-step and he came through this game so that’s very good news for us."