December has always been an interesting month every season and a lot of teams struggle during this period. I think the biggest loser this time is Newcastle United which lost 4 out of their 5 matches this month. They will be facing Liverpool the first week of January so another loss is more than likely to happen.
Man United caught a lucky break against Villa which is much needed as they battle for the top 4.
Boxing Day is a nightmare for teams that don't have an even composition of players, like Newcastle which has been on the rise in the last few seasons, the quality of their main players is quite good but this is not supported by an adequate second skuad at this time, I not to be surprised if Newcastle main squad experienced a decline in performance due to a busy schedule and not enough rest, I think that as a very rich team at the moment, Newcastle are still not ready to face a busy schedule of matches so the result is as you said, 5 matches 4 defeats.