Activision expects that Call of Duty: Black Ops will sell 20 percent less units than last year’s Call of Duty: Modern Warfare 2. The estimate comes via guidance released on the back of the publisher’s financial report last week.

Nonetheless, the projection still puts sales of Call of Duty: Black Ops at a gargantuan 13 million units.

Ubiquitous games analyst Michael Pachter also expects Black Ops to receive poorer reviews than Modern Warfare 2: “This year's game faces competition from holiday sales of Medal of Honor and Halo: Reach, both quite competitive in the shooter genre.

“Notwithstanding our concerns about the likely Metacritic score for Black Ops, we fully expect the game to sell in line or above our estimate of 13 million units, or three million below Modern Warfare 2.”

Earlier this year, Activision’s Mike Griffith said Black Ops was unlikely to perform as well as Modern Warfare 2 due to tough comparisons between the two.

Call of Duty: Black Ops goes on sale today.