BOSTON – As Al Horford wrestled with the biggest decision of his career last summer, he often circled back to one question: Where can I win? Horford had a productive nine-year career in Atlanta, a city, a community, he loved, and felt strongly about going back. But there was Boston, with its young core, its respected coach, its treasure trove of assets that put the Celtics in a prime position to not just improve on last year’s 48-win season but become a true threat to Cleveland in the years to come.

“It’s something I thought about a lot,” Horford told The Vertical. “You look at your career, sometimes it’s not about the money necessarily. It’s more about what you want to accomplish in life. What do you want to do, what do you want to get out of it. I knew I wanted to be in a position to be on teams that could win a championship. In Atlanta we had a couple of good teams, but I understood, looking at my future, being here was the right thing.”

Horford is a Celtic, the four-year, $113 million man, and while Boston isn’t a threat to the Cavs’ conference supremacy just yet, make no mistake: They are inching closer. Horford is everything the Celtics lacked last season, a true post scorer, a versatile weapon who improves the team on both ends of the floor. Defenses that loaded up on Isaiah Thomas now must plan for another All-Star-level threat, an unselfish big man who can score from anywhere.

[Sign up for Yahoo Fantasy Basketball | Mock Draft | The Vertical | Latest news]

All across the organization, Horford-mania rages. Thomas calls Horford “the ultimate pro” and Amir Johnson has gushed over his skills, while Danny Ainge has likened Horford’s game to ex-Celtic Kevin Garnett. Even-keeled Brad Stevens glows when asked about the elements Horford brings to the table.

“Before we signed him, we felt like he was the perfect fit for how we wanted to play,” the Celtics’ fourth-year coach told The Vertical. “And everything has been validated. The ability to quickly move the ball and make the right decision — the ball never sticks with him. We told him when he first got here that we just wanted him to be the best version of himself. He knows what he is good at and he is a great model for our younger players.”

Cleveland’s stranglehold on the conference remains tight, yet Boston continues to look like a team poised to eventually compete with the Cavs. The Celtics are young and talented, with the potential to be so much more. Explosive rookie Jaylen Brown figures to be a rotation player this season, and more young stars could be right behind him. The Nets have the look of a sub-20 win team, and Boston has the right to swap picks with Brooklyn next summer — and outright take the Nets’ pick in 2018. No team is more aggressive in trade talks than Ainge and his top lieutenants, and those picks will be mouthwatering assets to teams looking to offload high-priced stars.

For now Boston will fight for the top spot in the second tier, to muscle past the likes of Toronto, Atlanta and Indiana for the conference’s second seed. Player development is a priority in Boston this season. Evan Turner, a productive second-teamer, is gone, and the difference between 50 wins and a third or fourth seed and 55 and a No. 2 may hinge on the ability of Marcus Smart, Terry Rozier and Brown to replace him.

They will be supported by Horford, by a star uninterested in the spotlight, by a team-high plus-64 player in the preseason who will transform Boston’s frontline from one-dimensional to one dangerous in many ways. Horford says the transition to his new team has been easier than expected, and that he’s eager to develop the same chemistry with Thomas that he once enjoyed with Jeff Teague in Atlanta.

“They are two different players,” Horford said. “Isaiah is such a versatile player. He can really score the ball and is a really good passer as well. The similarities they have are that they both have a high motor. Isaiah is a really hard worker, and he has that drive, that edge that makes him a really special player.”

It has been three years since Boston dismantled the core of its title winning team, and really it seems so much longer. The roster has been rebuilt, the future largely secure. Horford isn’t the final piece of the championship puzzle, but his presence has moved the Celtics one step closer to completing it.

More NBA coverage: