Al Horford agrees to 4-year, $113M deal with Celtics, sources say

— -- Free-agent big man Al Horford has announced that he is heading to the Boston Celtics.

Horford and the Celtics agreed to terms on a four-year, $113 million deal, league sources told ESPN's Brian Windhorst.

The Atlanta Hawks had offered Horford five years, $136 million, which was less than the max, the sources said. The Hawks will halt trade talks on forward Paul Millsap and intend to keep him, according to the sources.

Horford also revealed the news on his Twitter account on Saturday.

Horford, an unrestricted free agent, has played his entire nine-year career in Atlanta, which drafted him third overall in 2007. The four-time All-Star averaged 15.2 points, 7.3 rebounds and 3.2 assists this past season.

After the Hawks were swept by the Cavaliers for the second straight year, Horford stressed just how much he has enjoyed playing in Atlanta and that the team still can win with some improvements to its current core.

"There are a lot of things that we need to address," Horford said of talking to his family and advisers. "But the biggest thing for me is I feel good here. I have a great relationship with coach ( Mike Budenholzer). That is important to me. And my teammates.

"Atlanta is a city that welcomed me from the first day... I'm very grateful for people that have always been real positive toward me and my family. I feel good. I feel like the way the team is going, I feel like we can win here."

Horford was the topic of trade rumors at the deadline, with the Boston Celtics reportedly being among those interested.

The 6-foot-10 center, who turned 30 in June, was expected to draw interest on the free agent market for his ability to shoot from the perimeter.

Last season, Horford shot a career-high 256 3-pointers after taking a total of 65 attempts in his previous eight seasons.

"I probably got a little away from the post this year trying to expand my game and do different things," Horford said. "That is a point of emphasis that I will try to be better in the post and be able to put the ball down a little more on the floor. Being able to drive a little more. Even though I had some strides in that area this year, I think I can be even better at that."

Information from ESPN's Ohm Youngmisuk was used in this report.