Average hours spent by Xfire users daily playing World of Warcraft have dropped by nearly 18 per cent from August numbers, according to data from the community and data application for the month of September.
It sets a pattern which is mirrored across many of the other top ten MMOs, with second-placed Guild Wars showing a 13 per cent drop and third-placed Silkroad Online falling over 27 per cent.
One of the likely main reasons for the drop is the end of the summer holidays for schools and colleges across Europe and the US.
Other key MMO titles remained relatively static, with MapleStory, Flyff and Eve Online taking fourth, fifth and sixth places respectively. Lord of the Rings Online remained in eighth place.
The top ten first-person shooters have also fallen across the board, although there was no change in the top five most played titles.
Call of Duty 2 Multiplayer and Counter-Strike Source took the top slots convincingly, although they lost around 12 per cent and 18 per cent of their audiences respectively.
Battlefield 2, Wolfenstein: Enemy Territory and Counter-Strike 1.6 rounded off the top five.
September's bonus statistic compared all World War II games, and unsurprisingly Call of Duty 2 Multiplayer was also top of that list, with other Call of Duty titles also taking third and fourth places.
Xfire is an application which tracks gameplay statistics for its user base of over 8 million, based mostly in Europe and North America.