When you hear the term “circled game” tossed around in sports betting discussions, it refers to the sportsbook method of limiting the betting action for a specific game. A “circled game” cannot be included in any exotic bets such as teasers or parlays and will only be available to bet on its own.
There are almost an infinite number of reasons that sportsbook resort to circling games, but in my experience the main reason is an injury to a key player, the effectiveness of said player, or if he is even going to be able to play.
Another reason for circled games could be the weather. If the weather is bad enough to impact the outcome of the game, or force the game to be rescheduled the next day (think double header in baseball), sportsbooks are usually ahead of the elements and limit the betting action.
If they didn’t do this, the sportsbooks could be vulnerable to someone who knows what they are doing and that has the bankroll to try and get the better of the book.