Al Horford ended the waiting game with a simple tweet: "Celtic Pride," it said, followed by 18 shamrocks.

The number might not have been a coincidence.

A franchise with 17 NBA championships may have gotten closer to contending for an 18th on Saturday, when Horford decided to accept a four-year, $113 million offer to join the Boston Celtics. Horford made the announcement on Twitter, and the terms of the detail were confirmed to The Associated Press by a person with direct knowledge of the negotiations.

The person spoke on condition of anonymity because no deals can be finalized until at least July 7 under league rules.

Horford wasted no time in changing his Twitter bio, which now says he is "Boston Celtics star Forward/Center Al Horford." And the reactions came in swiftly as well, after one of the biggest prizes in this year's free-agent sweepstakes decided to leave Atlanta.

"Let's get it," Celtics guard Isaiah Thomas wrote.

The Celtics won 48 games last season, finishing in a four-way tie for the third-best record in the Eastern Conference. They have a strong young core already, a highly regarded coach in Brad Stevens, and had the money to land a huge free agent.

Horford's announcement came on the same day that the Celtics met with Kevin Durant in New York, even bringing New England Patriots star quarterback Tom Brady along for that meeting to help sell the virtues of playing in New England.

No such fanfare was needed for Horford - just an average salary of about $28 million a year for the next four years.

Horford also met with the Washington Wizards as well as the Hawks, the team that drafted him and the team he's now leaving. Horford spent his first nine NBA seasons in Atlanta, but the Hawks agreed to terms with Dwight Howard and Kent Bazemore on big-money deals, leaving them little room for their centerpiece.

The four-time All-Star averaged 15.2 points and 7.3 rebounds last season. He gives the Celtics a formidable presence on both ends of the floor as they try to vault into the top tier of the East. (Associated Press)