Al Horford’s Celtics career apparently has come to an end after three years with the club. According to a source close to the All-Star center, his representation has ceased discussions with the Celts on a new contract.

Though no further information was given, other league sources from the West told the Herald it is expected Horford will sign a four-year contract elsewhere. With free agents unable to sign until July 6, there remains a possibility that changes on certain teams (even the Celtics) between now and then could impact this move, but it appears to be rather firmly set as of this point.

Horford had until Tuesday to opt in to the $30,123,015 final year of the four-year deal he signed in 2016. He chose not to exercise that option, but as written here last month, his side was interested in coming in at a more team-friendly number for the 2019-20 season if the Celtics would be willing to tack on two additional years for the big man who turned 33 on June 3.

The Celts seemed willing, with the two sides engaging in talks along those lines, but the process toward that goal came to a fairly abrupt end.

If Al Horford signs as a free agent elsewhere, where will he play in 2019-2020? #NBAFreeAgency2019 @bostonherald with other choices — Boston Herald (@bostonherald) June 19, 2019

The NBA’s free agent negotiating period does not officially begin until 6 p.m. on June 30, but it is not uncommon for information to get through from teams to players prior to that. And while it’s not known precisely how Horford felt about the Celtics’ prospects moving forward as he seeks to win a championship in this latter stage of his career, it seems almost certain he is aware another club is willing to go to a fourth year with him.

Kyrie Irving’s expected free agent departure for Brooklyn, reported here last week, is not said to have had any effect on Horford’s decision. As well, Horford and multiple people around him have insisted he is happy with Boston and the Celtics organization. This therefore appears to simply be a move for a better chance at a championship with a club willing to pay him more on a longer-term contract.

As a result of Horford moving on, there are scenarios in which the Celtics could have salary cap space in the high $20 millions. But that doesn’t necessarily mean the club will be a major player in the free agent market this offseason.

With Irving’s expected departure, as well, the Celts are back into a rebuilding situation, albeit this time one with young potential stars Jayson Tatum and Jaylen Brown and NBA All-Defensive first teamer Marcus Smart already in the fold. The wild card is Gordon Hayward, who was an All-Star prior to his 2017 opening night injury and conceivably could be again.

But with three first-round draft picks Thursday night, one or more of which they’d like to trade away, and free agent decisions to be made on Terry Rozier and Marcus Morris, the Celtics now have a roster in even greater flux than what was expected with Irving’s exit.