return to training after injury

the last 3 weeks were spent recovering from tendoniti in my hamstring where it connects to the knee. previously i had done 9 weeks of gpp and was in very good shape, then my tendonitis flared up the last week on gpp and i have not run for 19-20 days, actually i have just done some drills and strides the last week but nothing substantial. i have been biking and lifting the whole time off. so, my strength is fine, but i feel my aerobic conditioning has suffered a little, plus my legs need to get going again.

my question is:
should i using like 3-4 weeks of gpp to get back to where i was or only do like 1 week and go into spp1, i am going to use the 400 l-s. my indoor season starts the middle January and ends in the beginning of march.
i was leaning towards doing the 3-4 week gpp with one day being 2x300 with 7-10 min rest for the 4 weeks to keep the intensity lower but still transition smoothly into spp.

if figure this is a planning issue which is why i posted it here. i know the title makes it seem like the thread should be in revovery, but at this point that is not the problem as i am ready to start running again.
Hope i could get some advice.