After signing with 76ers, Al Horford thanks Celtics fans

Al Horford averaged 13.5 points, 7 rebounds and 4.6 assists in three seasons with the Celtics.Barry Chin/Globe Staf/Globe Staff

LAS VEGAS — The 76ers officially signed forward Al Horford to a four-year, $109 million deal on Wednesday. The former Celtic posted a message on Twitter about his three-year tenure in Boston.

“You welcomed me with open arms 3 years ago,” he wrote. “We had a goal to raise another banner in the rafters. We fell short of that goal. I appreciate everyone in Boston. Ownership, front office, coaches and teammates. Most important, thank you to all the fans. Thank you Boston!”

Thank you Boston! ☘️💪 pic.twitter.com/0uNk2OcRvd

— Al Horford (@Al_Horford) July 10, 2019

Horford signed a four-year, $113 million contract with the Celtics three years ago. He had a player option for next season, and after last season ended with a disappointing loss in the Eastern Conference semifinals, he said his preference was to return to Boston. But contract negotiations with Boston crumbled in mid-June, and Philadelphia stepped in with a massive offer that the Celtics were never willing to equal or exceed.

“He has built his reputation around hard work and a tradition of winning, which are the same qualities that have formed the foundation of the 76ers,” Philadelphia general manager Elton Brand said in a statement. “Al’s playmaking, elite defensive talents and veteran leadership confirm why he is a crucial addition to our roster. We have gained a championship-level teammate that will not only complement our current makeup, but will help grow our young core as we strive for the highest level of success.”

Horford averaged 13.5 points, 7 rebounds, and 4.6 assists in 208 regular-season games with the Celtics. Boston reached the conference finals in each of Horford’s first two years before the expectation-filled 2018-19 season ended with a five-game loss to the Milwaukee Bucks.

“Obviously, Al was great here,” Celtics coach Brad Stevens said Tuesday night. “We loved Al, we wanted him back. Again, it’s his choice. He can go do what he wants to do and there’s a lot of factors that end up helping these guys making those decisions. But he’s a heck of a player and did a great job here in the three years he was here.”