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The Philadelphia 76ers and the Sacramento Kings are expected to be among the "surprise bidders" for free agent Al Horford this summer, according to ESPN's Ramona Shelburne and Brian Windhorst.

The two noted that the Dallas Mavericks and New Orleans Pelicans are also potential landing spots for the center.

Horford recently decided not to exercise his $30.1 million player option for the 2019-20 season. Initially, that did not appear to be a move that signaled an end to his time in Boston, as Steve Bulpett of the Boston Herald reported the two sides had discussed a multiyear deal at a lower number.

However, Bulpett later wrote that the 33-year-old big man was expected to sign a four-year deal elsewhere. Marc Stein of the New York Times added that the belief around the league is Horford has a four-year, $112 million offer from a mystery team waiting for him in free agency.

Stein noted that offer is not expected to come from the Mavericks.

According to Shelburne and Windhorst, Sacramento is interested in adding a center to fill out a roster that already features point guard De'Aaron Fox and forward Marvin Bagley III. Philadelphia also reportedly has interest, though the Sixers' focus may be on their own free agents in Jimmy Butler, Tobias Harris and JJ Redick.

Horford figures to generate no shortage of interest as he played a key role in the Celtics' success in recent years. He is coming off a season in which he averaged 13.6 points on 53.5 percent shooting, including 36.0 percent from three-point range, 6.7 rebounds, 4.2 assists and 1.3 blocks per game.

With Horford stepping up, Boston came within one game of the NBA Finals in 2018 despite All-Stars Kyrie Irving and Gordon Hayward being sidelined due to injuries.