BOSTON (AP) — The Boston Celtics say center Al Horford will sit out Wednesday night’s game against the Chicago Bulls after being placed in the NBA’s concussion protocol.

The team says in a statement that Horford reported being hit in the head Monday during practice but did not exhibit any symptoms that evening or during a pre-practice period on Tuesday. But he was removed from practice later Tuesday after showing symptoms of a concussion.

Horford, who signed four-year, $113 million deal with Boston this offseason, has started all three games for the Celtics this season and is averaging 12 points and 5.3 rebounds per game.