FOXBOROUGH — Bill Belichick’s Friday morning news conference had just reached its 21st minute when a Patriots public relations staffer figured that was enough for the day.

“All right, guys,’’ he called out, signaling the end of the news conference.

But not everyone was ready to leave.

“I’ll take a couple more if you want,’’ Belichick said. “I know I had a couple of long answers there. You know that’s usually a problem with me — just going on and on and on.’’

Belichick has been known for giving expansive answers in his Friday news conferences. And he has been chatty all week, giving a lengthy response Tuesday about why he is no longer going to use the Microsoft tablets on the sideline and instead will go back to using hard copies of photos.

But whether he was pleased with the Patriots’ preparation ahead of Sunday’s game against the Steelers, or he just felt like giving a history lesson about the 1970s Steelers, or he was just practicing his Grandpa Bill stories, this Friday news conference was epic in its length and depth.

It officially lasted 29 minutes, 12 seconds, with Belichick casually dropping the names of Bill Russell, Mick Jagger, Chuck Noll, Tom Landry, Lou Gehrig, and the entire 1970s Steelers lineup on an unexpected media corps.

“Extending the play,’’ he joked at the end. “A little scramble.’’

It started off harmlessly enough, with a question about Rob Ninkovich and how he compares with former Pat­riots linebacker Mike Vrabel. That led into a question about Dont’a High­tower in which Belichick broke down the defense of the Alabama team that won three national championships this decade, followed by an insightful answer about Malcolm Butler and his “desire to tackle.’’

“There’s a certain type of defensive back I think that has that mentality,’’ Belichick said. “If they catch one, then, ‘I’m really going to try and tackle a guy as hard as I can because he caught one on me,’ type of thing.’’

Then about 10 minutes in, Belichick was asked how much respect he has for Noll, the longtime Steelers coach. This question really got him rolling, as he rattled off 787 words about the connections he’s had to the Steelers organization via his father, Steve Belichick, and fellow coaches Jerry Glanville and Rollie Dotsch, who coached the Patriots’ linebackers from 1974-76 and then worked with Belichick with the Lions in 1977.

At this point, about 15 minutes into the news conference, the PR staffer announced that there would be only two more questions. The next one was about Belichick breaking into the NFL in 1975 right while the Steelers were in the middle of their dynasty.

“Yeah, so on that note — in ’75 with the Colts, we started out 1-4 and we won the last nine games to go 10-4 and win the division,’’ said Belichick, recalling how his Colts then lost to the Steelers in the playoffs.

“I mean, they were so good on defense. Every guy was better than the next guy. From [Joe] Greene to [Jack] Lambert, that whole front four, and then the secondary, and offensively,’’ Belichick said.

“When you’re a young coach and you’re looking at, OK, who does things in a way that you admire or respect or want to emulate, or what can you take from a good program to help you as a coach, or if you ever get a chance, what would you do that they do? They were one of those teams.’’

Belichick then apologized.

“Not to cut you off on a question, but yeah, from the first year, the Steelers had a very strong impact from the outside on my philosophy as a coach,’’ he said in summation.

Then Belichick was asked what it was like to game plan against the Steelers in the ’70s.

“I was on the defensive side of the ball,’’ he said, “so with [Lynn] Swann, [John] Stallworth, [Franco] Harris, [Rocky] Bleier, [Terry] Bradshaw, it was, [Mike] Webster. I mean you could go right down the line, one Hall of Fame guy after another.’’

After detailing for another five minutes all of the advancements the Steelers made in the 1970s — becoming one of the first teams to develop a system on both offense and defense, and one of the first to institute a strength-and-conditioning program — Belichick came back to the present.

He was asked about safety Duron Harmon, and gave a fascinating answer about Harmon being a “silent leader’’ on the defense.

“I would say, and Bill Russell taught me this, that in a way, a silent leader in some respects is more powerful than a more vocal leader,’’ Belichick said. “There are guys that give you that quiet leadership that in a way is more powerful, because it’s not quite out there as much, but it’s that quiet push that sometimes can maybe have a little more impetus.’’

And when did Belichick meet Russell?

“Bill came here in 2002, maybe,’’ Belichick said. “We’ve spoken a few times. In fact, I saw Bill last year at the playoff games, at the playoffs with the Celtics.’’

Then came a question about Elandon Roberts, and the difficulty in scouting college players who don’t get a ton of playing time in school, and Belichick’s answer came completely out of left field.

“I guess the one that sticks out the most for me would be coach [Nick] Saban’s story about Lambert, when he was at Kent State,’’ Belichick said. “He was a backup linebacker and didn’t play. The kid in front of him [Bob Bender] was really their leader, he was kind of the heart and soul of the Kent State defense.

“Anyways, the kid dropped out of school, went to work for Mick Jagger, he was a security guy on tour with the [Rolling] Stones, and Lambert became the starting middle linebacker. He probably would have never played had that not happened, and you know, you have a Hall of Fame player.’’

And finally, after speaking 4,264 words at the podium, Belichick was done. Just another Friday NFL history lesson in the books.

Ben Volin can be reached at ben.volin@globe.com. Follow him on Twitter @BenVolin.