Howling:A sontaran called Strax

I'm a bit confused with the onscreen appearance of Strax in a Good man goes to war. This was the first on screen appearance of that character who was killed off towards the end of the episode however in a recent article, its stated that he makes an appearance in the 2012 Christmas special. This could be the first meeting between the Doctor and Strax of where the doctor saves his life. Wouldn't the meet take place in the doctors past but for the viewers it would take place in his future?