EXCLUSIVE: CBS is about to find out how big a hit it has on its hands with Blue Bloods. I’m hearing the freshman Tom Selleck drama — which has been averaging a healthy 12.3 million viewers on Fridays at 10 PM — will get a four-week trial run on Wednesdays at 10 PM beginning Jan. 19. Fellow freshman series The Defenders, which is currently occupying the Wednesday 10 PM slot, will shift to a new regular time slot, Fridays at 8 PM, starting Feb. 4. There, the legal dramedy will succeed departing paranormal crime drama Medium. Beginning Feb. 16, spinoff Criminal Minds: Suspect Behavior takes over on Wednesdays at 10 PM where it will follow Criminal Minds. This is the same strategy CBS successfully used for the launch of spinoff NCIS: LA, which also followed  the mothership NCIS series on Tuesdays. Blue Bloods, meanwhile, reclaims its Friday 10 PM post on Feb. 11. CBS, which declined to comment for this story, is expected to announce its midseason plans later today.