Robert Williams and the Boston Celtics have agreed to a four-year, $54 million contract extension.

Williams had 13 starts in the 52 games he played last season, when he averaged 8.0 points, 6.9 rebounds, 1.8 assists and 1.8 blocks in 18.9 minutes per game, all career highs.

The contract puts Williams among the top half of centers in the NBA in terms of annual salary.