Breaking News: Boston Celtics reach agreement with Al Horford to 4-year $113 million max deal

Danny Ainge got his guy, as the Boston Celtics reached agreement with All-Star big Al Horford to a 4-year, $113 max deal. He will receive a player option in the final year per ESPN's Ramona Shelburne. Horford is one of the most versatile bigs in the league, providing the interior presence the Celtics have desperately needed. The newest Celtic announced the signing on Twitter at the exact same time it was reported by Adrian Wojnarowski of The Vertical.

Celtic Pride!!!!!!

— Al Horford (@Al_Horford) July 2, 2016

With Woj controlling the NBA news universe for the past 48 hours, the Horford announcement was a sudden seismic shift after Woj had tweeted minutes earlier that the Celtics had "rapidly lost hope" and Horford was shifting toward an Atlanta return. He reported that the Hawks and Horford were around $6 million apart in negotiations, even though Horford had reportedly been willing to drop his demand for a fifth year.

Horford earlier in the day had apparently preferred the Wizards' roster, but eventually came around on the Celtics per Woj. The Thunder reportedly tried to pitch Horford, but the uncertainty over Kevin Durant and Russell Westbrook's futures became a breaking point.

Horford's father, Tito, told the Boston Globe's Adam Himmelsbach that Al was choosing between the Hawks and the Celtics. But the Celtics' fan base, when juxtaposed to the infamously dispassionate Hawks crowds, became a crucial factor. As a former NBA player who even tried out for the Celtics in 1995, the whole family had a great appreciation for the environment in Boston.

"There wasn't as much motivation for him when he saw all the empty seats when they were winning." the senior Horford told the Globe. "He said to me, 'Dad, when we were playing Boston, they were down 15 points and they were cheering their team like they were winning the game. They're so into the game.' This is special for us, especially him."

The Celtics received the news that Horford was picking them while their plane was taxiing on the runway as they were leaving the Hamptons, per the Globe. They had completed their Durant meeting and were about to take off to Boston when the call came through.

"It covered every aspect of life on and off the court in Boston and our team's future," a team source told the Globe. "We just made it clear from the beginning that there was a real connection."

The connection was real, as the Horfords state that Boston has always been enticing and became the destination after their meeting. "Ever since Boston, Danny Ainge and the whole organization began to show interest in him, that opened his eyes," Tito Horford said. "He always had a good feel about Boston."

Horford signing is a crucial turning point for the franchise, as he is the first All-Star free agent in generations to sign with Boston. It proves the Celtics' risky model can work, as their cap space has become a useful tool in addition to their more tangible assets.

"I think that Al has signaled his intentions to be a Celtic is really a historic step for this franchise," a team source said. "To take a 48-win team with a young core and a great coach, and you add a four-time All-Star as a max free agent, and you can just see the direction we're going in."

Signing Horford gives the Celtics a crucial boost in the Kevin Durant sweepstakes, killing two birds with one stone. It would allow the Celtics to pitch Durant on teaming up with Horford and Isaiah Thomas while preventing the Thunder from dangling a potential move for Horford to entice Durant back to Oklahoma. Even if Durant returns to Oklahoma for one year as has long been expected, the Celtics signing Horford would at least set the stage for round two of the Durant pursuit next offseason.

"We're thinking big, and this is a big move," the Globe's source said. "This will set us up for the future in a better place."

Durant plans to decide on his future within the next 24-36 hours according to ESPN's Chris Broussard in what will be the biggest moment of the offseason in the NBA.

Horford gives the Celtics their first truly dynamic big since Kevin Garnett. While Amir Johnson proved to be one of the most efficient post defenders in the league this year, Horford is one of the truly elite bigs in the league. He is one of the most consistently effective shot effectors in the paint, while excelling in both icing and switching in the pick-and-roll.

Horford is a great passing big who allows the Stevens system to flourish by serving as a distributing hub in the offense. After drafting Jaylen Brown, adding Horford gives the Celtics yet another great transition player for their position. Horford has a strong history of both initiating fast breaks and as a ferocious finisher in transition.

Offensively, Horford has a long track record of being a great post scorer while being a knock-down midrange shooter. Horford shot 47.0 percent from midrange and 34.4 percent from three last season, although he struggled with his outside shot a bit in the playoffs.

Perhaps the biggest advantage to adding Horford is that he will replace Jared Sullinger in the starting lineup while having a very similar playing style. The outside shots that the Celtics force fed to Sullinger will be bread and butter work for Horford. They will ask him to take a step back from his preferred 20-foot space to get his toes behind the three-point line, which Horford should be willing to try. Horford shot 88-for-256 (34.4-percent) in his first season as a consistent three-point shooter, compared to Sullinger's 81-for-287 (28.2-percent) over the last two seasons.

Horford is a fantastic scorer in the high-post, both with his back to the basket and facing up. He has the passing vision necessary for a post scorer to be viable in their system and can dribble out of double teams as well. Horford gives the Celtics their first big since Garnett who can facilitate and closeout the offense from any point on the floor.

Committing a four-year deal to a 30-year-old is a risky proposition, but Horford has remained healthy throughout his career and has continued to expand his game as he passes through his prime.

The Celtics can now turn their attention to dealing with the strong possibility that Durant chooses to return to Oklahoma for one season. They have the option to keep Johnson and Jonas Jerebko for one more season at great value, but there are still worthy alternatives to Durant on the market. They could make a max offer to Harrison Barnes to compete with the Dallas Mavericks, but it is widely expected that the Warriors will match that offer if they also strike out on Durant. After drafting Jaylen Brown, the Celtics have minimal pressure to sign a swingman this offseason if Durant falls through.

Keeping Amir Johnson is a viable option as he can both start next to Horford or be one of the best bigs coming off the bench in the league. Jerebko is an easy choice to keep if his $5 million in cap space is not required, considering he would be worth at least twice his salary on the market.

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And for a live look in on Celtics fans...

THE CELTICS SIGNED AL HORFORD pic.twitter.com/Xg8ejg0Mc8

— Kyle George (@kyoo) July 2, 2016

In Nike store and #Celtics fans start cheering. Tell cashier Horford is biggest FA signing ever for team. He replies "Nah man, @Scalabrine."

— Jared Weiss (@CLNS_JaredWeiss) July 2, 2016