The move came about because on Monday, rival network ABC shored up its Monday schedule by securing simulcasts of ESPN’s Monday Night Football for the remainder of the season it didn’t already have, after moving Dancing with the Stars to Tuesdays. By the time NCIS: Sydney arrives on the schedule, that would have covered weeks 10 to 15 of the regular season depending on what CBS’s holiday festivities are looking like. That either side of the battle is happening at all is because the studios refuse to meet with their striking writers and actors of the Writers Guild of America and SAG-AFTRA, and are only just doing so this week after over 140 and 70 days respectively, and so a lot of this season’s scripted series don’t have episodes produced yet this season.
In the Monday slot, Sydney was following a repeat of NCIS, and a second repeat will now be taking that slot. CBS is relying on its arguably most resilient repeat performer while biding time for both active American series to get back into production. The Tuesday slot will have been just left by Big Brother, which will have completed its season presumably the previous week. NCIS: Sydney, which stars Olivia Swann, sees rising international tensions in the Indo-Pacific. The brilliant and eclectic team of United States NCIS Agents and the Australian Federal Police (AFP) are grafted into a multi-national taskforce, to keep naval crimes in check, in the most contested patch of ocean on the planet.

