Bill Belichick was assured by his book publicist just days before his now-infamous sitdown with “CBS Sunday Morning” that his interview for the show would closely stick to topics related to his new book … TMZ Sports has learned.

Sources familiar with the situation tell us … back on April 9, Simon & Schuster’s senior director of publicity, David Kass, wrote to Belichick, “I can assure you that the conversation [will be] about the book.”

“This is a book segment,” Kass added, “that looks at your life in football and what people can learn from you to achieve success in their own lives.”

On April 21, just less than two weeks after that message was sent, Belichick fielded no fewer than six questions from Tony Dokoupil for the CBS segment that appeared to be unrelated to his new “The Art Of Winning: Lessons from My Life in Football” work.

Four of them surrounded his relationship with Robert Kraft — who was not mentioned in the Belichick tome. Others, we’re told, involved Belichick’s portrayal in “The Dynasty: New England Patriots,” a popular 2024 TV miniseries. At least two other inquiries centered around his personal connection with his girlfriend, Jordon Hudson.

Our sources say Belichick was furious … as even though it was expected there would be potential questions about Kraft and Hudson, he anticipated them only being related to their roles in his book, or in Kraft’s case, lack thereof.

Sources say Belichick had actually shot down several interview opportunities Kass had put in front of him over concerns the media outlets would use his book promotion as a way to pry into subjects not related to the actual book.

We’re told Belichick had even at points wanted to turn down CBS … but Kass was adamant he do it, writing to the 73-year-old, “I wouldn’t be this insistent if this wasn’t so important to book sales and without risk.”

Kass, our sources say, actually flew to North Carolina on March 20 to encourage Belichick to go along with their marketing strategy. Then, in the days following their in-person meet-up, Kass ensured Belichick in writing that he had talked to a CBS producer “about sticking to the book and shared that if they do, they’ll get a great interview, and he was really open, saying he’s not interested in going beyond the book.”

Kass did warn Belichick on March 26 “there would likely be one question about what you’re up to now.” Additionally, on April 8, he stated CBS would not provide any questions to them in advance, clearly making Belichick aware there was at least some chance of surprises. Kass also, we’re told, offered at least once to set up a call with a show producer so they could “talk things through” before Belichick got in the interview chair.

But according to sources, Kass ultimately wrote to Belichick the “CBS Sunday Morning” segment would be a “puff piece” that was “designed to make everyone look good and sell books.”

We’re told Kass did not go with Belichick to the interview, which took place at Bill’s former high school, Annapolis H.S. in Maryland. Our sources say Kass opted out, writing to the coach’s team he “had asked Bill if he wanted me there and he didn’t seem to care, so I thought it best to stay back and not lose all that time in transit.”

In Kass’ absence, Hudson — who sat near show producer Gabriel Falcon during filming — took it upon herself to speak out and try to steer the Dokoupil interview back toward book topics. Our sources say Hudson actually attempted to call Kass as things got off track, but she could not get in touch with him.

The final cut ended up airing on April 27 … and it drew so much negative publicity, Belichick released a statement to try to explain what he believed caused it all to go so sideways.

“Prior to this interview,” he wrote, “I clearly communicated with my publicist at Simon & Schuster that any promotional interviews I participated in would agree to focus solely on the contents of the book.”

“Unfortunately, that expectation was not honored during the interview. I was surprised when unrelated topics were introduced, and I repeatedly expressed to the reporter, Tony Dokoupil, and the producers that I preferred to keep the conversation centered on the book. After this occurred several times, Jordon, with whom I share both a personal and professional relationship, stepped in to reiterate that point to help refocus the discussion.”

He continued, “The final eight-minute segment does not reflect the productive 35-minute conversation we had, which covered a wide range of topics related to my career. Instead, it presents selectively edited clips and stills from just a few minutes of the interview to suggest a false narrative — that Jordon was attempting to control the conversation — which is simply not true.”

Hudson, too, tried to shed light on the situation after the show aired … posting on her Instagram page an April 10 email Belichick had sent to Kass and others that showed her boyfriend emphasizing he wanted to promote “The Art Of Winning” without addressing “all the current events that don’t have anything to do with the book.” She added a Taylor Swift song to the IG post that appeared to be a jab at Kass — “Look What You Made Me Do.”

CBS ended up releasing its own statement on everything, writing, “When we agreed to speak with Mr. Belichick, it was for a wide-ranging interview. There were no preconditions or limitations to this conversation. This was confirmed repeatedly with his publisher before the interview took place and after it was completed.”

Kass has yet to publicly address the situation. Simon & Schuster, meanwhile, declined to comment when we reached out on Tuesday.

Prior to joining Simon & Schuster, Kass worked as the vice president executive director of publicity at Hilsinger Mendelson, where he described himself as “a straight shooter whose word can be relied upon.”

In his bio on Simon & Schuster’s website, Kass — who once helped Jeff Benedict‘s Robert Kraft-themed book, “The Dynasty,” reach the New York Times’ bestseller list — stated he has a passion for “orchestrating meaningful publicity campaigns for titles that serve a larger propose, uncover truths, and tell great stories.”

“He sees book publishing and the associated media campaigns as an opportunity to truly change minds,” the bio reads.