Jenkinson now faces a spell on the sidelines.
Gunners boss Arsene Wenger explained: "Carl has a stress fracture in his back. That's just about rest now. We discovered that because he had a pain in his back. First you monitor it, then play a little bit and then you check again because you are cautious.
'We found a small stress fracture that we noticed at an early stage. If he continued to play it could have got worse and then he could be out for a long time. So at the moment the specialist has decided to rest him."