They have been lucky with injuries, certainly. Even though Ox, Podolski, Walcott and others were missing at the same time, they had just enough depth to cover it. 5 points in not unassailable though, especially over the busy Christmas period. Losing Giroud, Koscielny or Szchezny would hit them hard as the backup options are a big drop in quality.
Then again, the only teams with true depth are Chelsea and City, and they have been pants so far.
I just hope that my lot, Liverpool, keep it up for the rest of the season and strengthen in January.