Activision Blizzard is one of the biggest publishers in gaming, and it's stock is riding high currently. But one analyst has now come forward with a note to investors that details "a combination of worries" about the company's stock price. As a result, Cowen & Company has downgraded Activision from its Outperform rating to a lower rating. It's the first time in nine years that Cowen has downgraded Activision's stock, apparently.

Starting off, Cowen believes that investor expectations for Activision's performance is fiscal 2018 is "too high." Based on conversations with Cowen's clients, the firm believes industry expectations--of overall industry growth of 12-13 percent year-over-year--is "highly unlikely."

GS News Update: Call Of Duty: Black Ops 4 Officially Confirmed, Release Date Earlier Than Usual

In terms of specific concerns, Cowen said the Overwatch League--which starts up in earnest in December--may not be the revenue monster than investors are hoping for. Some investors see the Overwatch League as adding significant revenue to Activision Blizzard's bottom line, but Cowen says it's too early to say if this will be the case.

"We think esports [profit and loss] expectations for 2018 are low, but we also think OWL needs to demonstrate that it can attract a significant audience," the firm said. Cowen said it believes the first Overwatch League season will be "a learning experience," with better results later down the road. Indeed, Activision has spoken openly about how this first season is laying the groundwork for potentially bigger and better things to come in the future.

Another reason for Cowen's Activision rating downgrading is that the revenue from subsidiary King's advertising push "appears to be taking longer to launch than [it] had anticipated."

Overall, Cowen said it remains confident in Activision's core businesses. This year's Call of Duty: WWII should perform better than last year's underperforming Call of Duty: Infinite Warfare, Cowen said, while the firm also predicted that Call of Duty: Black Ops 4 will come out in 2018. [This has turned out to be true, and Black Ops 4 is real.] While Cowen is downgrading Activision's stock rating, it's important to note that no one can predict how Activision's stock with total accuracy. Indeed, Cowen acknowledged that Activision's stock could stay strong, especially if Blizzard launches a new title, potentially a Warcraft game for mobile devices or a StarCraft title.

If Blizzard is to announce any new titles, that could happen during BlizzCon 2017 in November. Keep checking back with GameSpot for the latest.

Activision Blizzard will release its latest quarterly earnings report on November 2, at which time the company will disclose key revenue and performance metrics. GameSpot will have a full rundown of those details at that time.