"Castle" season 8 has seen the lowest ratings in recent years, reports Cartermatt, so much so that it is speculated to be the main cause for episode 6 to be pushed back not one but two weeks. There are also speculations that despite new showrunners taking over, the low ratings may lead to the series's cancellation.

Season 7 saw an average rating of 1.6 million viewers in the 18 to 49 demographic per episode. This was even higher during season 6, which saw an average rating of 1.9 million. Season 8's highest rating thus far is reported to be a mere 1.2 million and the most recent episode saw a significant drop to just 1.1 million.

It is speculated that one reason for the drop in last episode's rating was due to "Castle" competing with the "Star Wars: The Force Awakens" trailer that aired on "Monday Night Football," which ran simultaneously against "Castle." However, even with this factor taken out of the equation, the season has only managed a high point of 1.2 million.

The report cites that fans speculate the drop in ratings may be due to the plot twist that forced Castle (Nathan Fillion) and Kate (Stana Katic) to separate, although it is explained that this might not be the real cause. Cartermatt states that the competition against the new time slot for "Castle" is partly to blame, particularly "Blindspot" and "Monday Night Football."

Another factor that may lead to the show's cancellation is the fact that the next episode, "Cool Boys," has been pushed back and is now set to air on Nov. 9. This will make it a full three-week difference from its air date to that of the previous episode, "The Nose."

Before season 8 was officially renewed, there were speculations that it might be cancelled due to the expired contracts of the main cast. New showrunners have been brought in and both Fillion and Katic have signed on but even that may not be enough to keep the series going for a tenth season if ratings continue to descend.