PLYMOUTH — When NBA free agency began in July and the basketball world turned its eyes toward Kevin Durant’s massive decision, many other players were left to wait patiently, hoping to capitalize on the windfall created by the ballooning salary cap.

Celtics backup center Tyler Zeller was coming off the most frustrating season of his four-year career. He played sparingly and was often left wondering where he fit in lineups that were often smaller and more skilled. And after playing just 11.8 minutes per game over 60 games, he was left to wonder how that year might have affected his future.

“The first week I thought would go pretty quick, and then the second week we’d kind of start to see some things happen,’’ Zeller said after taking part in the Celtics’ Shamrock Foundation golf tournament at Old Sandwich Wednesday. “And after about two weeks I’m sitting there like, ‘Nothing has happened. What is going on?’ ’’

Zeller called his agent every day, hoping there would be more clarity. He said they were in contact with several teams.

When the Celtics ultimately rescinded their qualifying offer for their other restricted free agent, forward Jared Sullinger, there seemed to be a fresh opportunity for Zeller. The 7-footer finally signed a two-year, $16 million deal, with the second year nonguaranteed.

Zeller is excited to return to a team that he is familiar with and to play for a coach he respects, but he also knows that last season was difficult, and that he should be prepared for anything.

“You never know what’s going to happen,’’ Zeller said. “I could play really well. Somebody could get hurt. All those things go into it.

“And at the same time it could be exactly like last year, so you kind of have to just go into it with an open mind and try to come into the season as prepared as possible to try to compete for one of those spots.’’

Lauding Horford

Celtics co-owner Wyc Grousbeck was at the NBA’s labor relations meetings in New York recently when he ran into Hawks guard Kyle Korver, who is one of the player representatives.

The Celtics, of course, signed Korver’s longtime teammate in Atlanta, Al Horford, to a four-year, $113 million contract in July, and that reality was not lost on Korver.

“Kyle just said, ‘You got our guy,’ and he was just shaking his head,’’ Grousbeck said. “It’s more for him to say than me. He congratulated us on getting a very good player.’’

Grousbeck said several people have told him about Horford’s leadership, and that the veteran already is making a concerted effort to bond with his new teammates.

“That’s what leadership is,’’ Grousbeck said.

Horford was probably the second-biggest signing of the summer, after the Warriors lured Durant.

“The thing that makes him so tough is he can do everything,’’ Zeller said. “He can post up, he can shoot the three, he makes plays off the dribble.

“He’s a very smart player, and I think he’s going to be great to be able to run our offense through at times, and just be able to make the right play.

“He’s not always trying to score. Sometimes he’s trying to draw two and be able to throw it to somebody for a three. And so he does a great job with setting screens, making plays.’’

The other side

Celtics coach Brad Stevens will be a guest speaker at the Bill Belichick Foundation’s Hall of Fame Huddle at the Seaport Hotel Friday. Stevens said the Patriots coach recently asked him to take part.

“You get an e-mail from Bill in the middle of football season, or in the middle of football preparation, it’s a pretty unique e-mail,’’ Stevens said. “But it’s obviously great. You feel pretty inadequate as a coach after you spend time with him. He knows what he’s doing.’’

Stevens said he has always been fascinated by football teams’ operations. When he coached at Butler, he spent a day with the Indianapolis Colts while Peyton Manning was their quarterback. More recently, he went to Columbus, Ohio, where he was coach Urban Meyer’s guest at a Buckeyes practice.

“It’s really interesting for me to see how people coach the team,’’ Stevens said, “because when you start talking about having that many guys around, and you start seeing how it’s organized, you start seeing how the head coach can’t be in every meeting.

“The head coach can’t be in every drill, he can’t be in every huddle, and you have to have a great deal of trust and delegation in your staff. And everybody moves at such an incredible tempo. It’s just a really well-organized machine.’’