Zynga's chief operating officer folded his cards on Wednesday, leaving the social games company just as heavyweight Amazon.com steps into the ring and rival Electronic Arts (EA) takes it to court.
John Schappert, who ran daily operations at the San Francisco firm behind hit games including "CityVille" and "Zynga Poker," left his post and the board of directors "effective immediately," according to Zynga.
"John leaves as a friend of the company and we wish him all the best," Zynga founder Mark Pincus said in a release confirming Schappert's departure.
"John has made significant contributions to the games industry throughout his career and we appreciate all that he has done for Zynga."
Zynga shares slid slightly less than two percent to $2.90 in the wake of the news.
Online retail colossus Amazon on Tuesday launched its first online social game in a challenge to Zynga and announced the creation of a Game Studios team actively seeking new talent.
The "Living Classics" title was tailored for play at leading social network Facebook, where Zynga rose to stardom.
Amazon has the capital and the online clout to "disrupt" the social games industry from small startups to established titans such as EA, according to Douglas McIntyre of investment website 247Wallst.com.
California-based Electronic Arts on Friday revealed that it had filed suit claiming Zynga's game "The Ville" introduced in June illegally copied "The Sims Social."
The Sims Social is among the life-simulation games from Silicon Valley-based EA.
Zynga vowed to fight the lawsuit.
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