CBS CEO Leslie Moonves sensed something was afoot when he sat down for a lunch in mid-July with his executive and friend of 25 years Nina Tassler in the private dining room off his office. In the past few years, Tassler had started to feel restless on her perch atop CBS Entertainment, taking on writing a book, optioning a play and a feature script. After some soul-searching, Tassler, at the beginning of 2014, signed a new four-year contract, getting a promotion from President to Chairman of CBS Entertainment.

“I was very relieved when she re-uppmoonvestasslered,” Moonves told Deadline. But, having developed a very close personal and professional relationship with Tassler over the past quarter-century, Moonves could see that “part of her was excited” about staying on, but she also was interested in pursuing other things.

And at their lunch two months ago, Tassler told him, “I know I have a contract, but I really feel it’s the right time for me to do something else.” After that, “there were a lot of tears on both our parts,” Moonves said, “I was talking to a dear friend.”

Tassler’s successor was determined at that very lunch, Moonves said. “The good news is we both knew an extraordinary executive who could take this job,” he said, noting that it was Tassler who first brought up CBS/CBS TV Studios’ head of current programming Glenn Geller. Despite the lack of development experience, Moonves called Geller “the obvious choice” for the President of Entertainment job, noting that no other candidates were considered. “His knowledge of all of our programming — primetime, late-night, daytime — is tremendous. … He has had a bigger and bigger profile internally,” Moonves said.

Glenn Geller, Executive Vice President, Current Programming for the CBS Network Television Entertainment Group. Photo: Sonja Flemming/CBS ©2013 CBS Broadcasting, Inc. All Rights Reserved.

The transition plan was put in place within days, and a time was chosen to make it public — the week after the high-profile premiere of CBS’ Late Show franchise with new host Stephen Colbert and the launch of the fall season. Then the proverbial CBS cone of silence was imposed, with only a handful in Moonves’ closest circle privy to the decision in order to keep it under wraps until today.

Moonves said that Geller had made an impression during the annual scheduling meetings, where a small group of top CBS executives gather together in New York in the days leading to the upfronts to discuss the network’s schedule for the following season.

“I was impressed by his analysis of shows, people and the schedule,” Moonves said. “I really respect his opinions, and he wasn’t afraid to disagree with me — which I like, despite some people thinking I’m this dictator.”

Geller also did well when tackling major problems on existing series that had to be brought to Moonves’ attention. “I love the creative discussions and how he handles himself,” Moonves said.

Image (3) cbs-logo__120711164808__121116195436__130108233101__130716162250__130926192712__131121001522__140312174530__140523013157.jpeg for post 735047CBS is heading into this development season with two new executives in top positions, probably the biggest executive turnover at the always-stable network since Moonves took over. Tassler’s top lieutenant, EVP Comedy Wendi Trilling, departed in May, replaced by her No. 2, Julie Pernworth.

“We have an extraordinary team — Julie was right there, and it’s been a seamless transition; I expect the same to happen with Glenn,” Moonves said, noting that there will be “no other major changes” coming in the CBS executive ranks.

“To the outside world, (Tassler’s departure) may be stunning, but inside CBS, it’s a pretty smooth transition.”