Injuries vs Team Age

The wonderful @MarkJFine spent some considerable time since the season started comparing the stats from the final injury table of the season and the average age of the teams in the league.  These are his results:

Seems to be quite a few discrete clusters with just a few outliers, which implies some kind of relationship(s).
Arsenal shows as the youngest and nearly the most injury prone next to Man United. This may imply a cause and effect, where younger inexperienced players were used due to the amount and severity of injuries.
Curious how Newcastle and Sunderland are close, as are QPR and Fulham, although on opposite ends of the spectrum which may imply similar recruiting and training styles due to their locale. Conversely, this is not the case with Liverpool and Everton, both Manchesters, West Brom and Aston Villa; as well as the remain...