New England Patriots quarterback Tom Brady felt trapped this past offseason and was not sure he wanted to play anymore for the only NFL coach he has ever had, Bill Belichick, according to a new book on Belichick's life.

"If you're married 18 years to a grouchy person who gets under your skin and never compliments you, after a while you want to divorce him," a source with knowledge of the Brady-Belichick relationship told ESPN's Ian O'Connor, author of "Belichick: The Making of the Greatest Football Coach of All Time," after the 2017 season.

"Tom knows Bill is the best coach in the league, but he's had enough of him. If Tom could, I think he would divorce him."

Based on interviews with 350 people (Belichick did not cooperate), the book, due out Tuesday, reports Brady was so upset with his coach that he still wasn't certain in late March if he would return to the Patriots.

"But in the end, even if he wanted to, Brady could not walk away from the game, and he could not ask for a trade," O'Connor wrote. "The moment Belichick moved [Jimmy] Garoppolo to San Francisco, and banked on Brady's oft-stated desire to play at least into his mid-forties, was the moment Brady was virtually locked into suiting up next season and beyond. Had he retired or requested a trade, he would have risked turning an adoring New England public into an angry mob."

ESPN's Seth Wickersham and several Boston outlets had reported on the escalating tension between Brady and Belichick during last season, much of it revolving around the coach's decision to reduce the team access that had been granted to Alex Guerrero, Brady's business partner and fitness coach. Belichick was no longer giving his quarterback the most-favored-nation status that he had enjoyed in the past.

New York Yankees general manager Brian Cashman recalled in the book that Belichick told him years earlier about a disagreement Brady had with a Patriots strength coach over equipment. "Belichick said, 'If Tom Brady wants it, Tom Brady gets it,'" Cashman said. "If you get a player at that level, you get him what he needs, even if the strength coach says otherwise."

Brady was the league's only starting quarterback who didn't attend voluntary organized team activities in the spring; he also was angered by the Malcolm Butler benching in the Super Bowl LII loss to the Philadelphia Eagles. Asked by broadcaster Jim Gray in late April if he felt appreciated by Belichick and owner Robert Kraft (with whom the quarterback maintains a close relationship), Brady responded, "I plead the Fifth! ... Man, that is a tough question."

The transactional relationship between the five-time champs, Brady and Belichick, had been reduced to a stare-down that didn't surprise those in the quarterback's camp. According to the book, Brady's family long felt Belichick would push out his longtime franchise player before he was ready to retire. Brady's sister Nancy is quoted telling people that her brother believed "Belichick will definitely do to him someday what the Colts did to Peyton [Manning]."

According to a new book on Bill Belichick's life, Tom Brady was so upset with the Patriots coach that he still wasn't certain in late March if he would return to the team. Fred Kfoury III/Icon Sportswire

Brady started worrying for his job almost immediately after Belichick cited his age and contract status -- and the coach's desire to be "early rather than late at that position" -- when the Patriots drafted Garoppolo in 2014. One New England assistant said the general feeling among staff members around that time wasn't that Belichick's system could make Super Bowl quarterbacks out of all 32 NFL starters. "But if you gave us any of the top 15, we could do it," the assistant said. "I don't think the coaches view Tom as special as everyone else in football does. Mr. Kraft thinks Tom is the greatest gift ever, but the coaches don't."

Other notable material in the book includes:

Deflategate

In the early days of the case, Belichick was among the Patriots officials who had "serious doubts" about Brady's claim he had no involvement in the potential deflation of footballs used in the January 2015 AFC Championship Game victory over the Colts.

One person close to Brady said his entire family was "miffed" at Belichick for telling reporters to ask the quarterback about his preferences on game balls and "very miffed" at Kraft for reluctantly announcing in 2015 that he wouldn't fight Brady's four-game ban. Of the notion that Belichick had initially dumped Deflategate in his quarterback's lap, one close friend of Brady's said, "I thought Bill handled it terribly, especially when it involved a guy who'd done everything to help your career as a coach, and you hung him out to dry."

Brady told friends that his weak answer to the news conference question about whether he was a cheater -- "I don't believe so" -- didn't betray a consciousness of Deflategate guilt, but rather thoughts of the earlier Spygate conviction and his belief that at least some of the suspicions over the years about alleged Patriots black-ops tactics were likely true.

Spygate

During the Patriots-Jets season opener in 2007, after a Patriots staffer had his camera confiscated for illegally filming Jets coaches from the sideline, three law enforcement officers refereed a heated debate in a Giants Stadium office over control of the camera and tape. FBI agent Bob Bukowski and longtime New Jersey state troopers and Meadowlands security officials Jim Crann and Pat Aramini, who had worked undercover to infiltrate the Genovese crime family, listened as Patriots security chief Mark Briggs and two Jets officials made what Crann called "cross allegations" of wrongdoing. Crann said Briggs kept accusing the Meadowlands officers of stealing New England's camera. Said Bukowski of the Patriots and the Spygate tape: "They knew what was on it, and they wanted it back. They were trying any reason, but there was no way."

Urban Meyer/Aaron Hernandez

While coaching at Florida, Urban Meyer warned at least one NFL team that it should not draft his talented but troubled tight end, Aaron Hernandez. Meyer told that team, "Look, this guy's a hell of a football player, but he f---ing lies to beat the system and teaches all our other guys to beat the system. With the marijuana stuff, we've never caught this guy, but we know he's doing it. ... Don't f---ing touch that guy." An official with that NFL team said he was taken aback when Meyer's friend, Belichick, drafted Hernandez in the fourth round. "I never understood that," the official said.

Bill Parcells

Parcells and Belichick had repaired much of the damage to their relationship caused by Belichick's stormy departure from the Jets after 1999, but Parcells is quoted in the book questioning why his former defensive coordinator's game plan in the Giants' Super Bowl XXV upset of the Bills ended up in Canton. "I don't know whose idea that was to put it in the Hall of Fame," Parcells said. "If anything should be in the Hall of Fame, it should be [offensive coordinator] Ron Erhardt's game plan. We had the ball for 40 minutes and some seconds. That takes work, consistent play. We were only on defense for 19 minutes. To me, we had a good game plan against them. It was well thought out, a couple of things we did, the two-man lines in that game. But I'm not diminishing anything. I'm just telling you. I don't know how that happened. I'm not knocking anyone here."

Nick Saban

Though the longtime friends formed a devastating tandem in 1994, when their Browns defense allowed a league-low 204 points, Belichick and Saban had their moments in Cleveland. Saban had little use for Belichick's restrictions on his assistants' access to reporters or for Belichick's conservative philosophy on defense. "Nick was so pissed with Bill," recalled Pro Bowl defensive end Rob Burnett. "He wanted to do so many things and he was hamstrung by Bill. I used to meet with Nick all the time, and Bill would not bend as far as changing defenses. He stayed as vanilla as ice cream. ... To Nick I was like, 'Oh, man, remember in training camp when they couldn't block us on this blitz?' He goes, 'I know, I know. But sometimes I put it in the game plan and Bill won't run it on Sundays.' ... At the end, it wasn't the best relationship."

Giants

Longtime Giants general manager George Young made it clear that the team's defensive coordinator, Belichick, would never succeed Parcells. "I was there when [Young] said it," recalled personnel man Chris Mara. "He said, 'He'll never become the Giants' head coach.' ... George, like others, said, 'This is an ex-lacrosse player. He's a disheveled-looking mess most of the time.' George was big on that other stuff as far as appearance, which is why he was so high on Ray Perkins, who took command of everyone around him and was a born leader. I just don't think he saw that in Bill Belichick."

Belichick's father