World of Warcraft: Mists of PandariaMassively multiplayer online role-playing game World of Warcraft has lost over one million subscriptions in the last fiscal quarter, publisher Activision Blizzard revealed today during its quarterly earnings conference call.

Subscriber numbers held steady for months at 10.2 million, but as of June 30, that figure dropped to 9.1 million.

Blizzard Entertainment President Mike Morhaime said during the call that, historically, the game has seen a usage decline toward the end of an expansion cycle. “We saw similar drops in subscribers in the months before Cataclysm,” he said, “followed by a substantial number of returning players around the Cataclysm launch.”

Morhaime also believes that a number of players took a break from WoW to play Diablo III. The third installment of the popular dungeon crawling franchise has sold more than 10 million copies since its mid-May release.

World of Warcraft’s struggles could be influencing Activision’s bottom line. Although the company beat expectations during its second quarter earnings report, its stock fell 2.29 percent in after-hours trading to $11.50 a share.

R.W. Baird & Co. analyst Colin Sebastian said the drop is tied, in part, to WoW’s subscriber levels, but believes the impact will be small. “Management indicated that the bulk of the decline came from Asia, which means there is less of an impact on revenues,” he said.

World of Warcraft’s next expansion, Mists of Pandaria, will launch on September 25. Activision Blizzard will début a cinematic trailer for the game during this year’s Gamescom event.

Electronic Arts’ Star Wars: The Old Republic, arguably WoW’s largest competitor, also recently lost subscribers, dropping from 1.3 million to less than one million in the first fiscal quarter ending on June 30. In an effort to boost those numbers, developer BioWare announced earlier this week that the game will become free to play later this year.