Rob Williams is finding his role as Celtics head into seasons final week

BOSTON — Heading into the last week of the regular season, a trip to potential second-round opponent Philadelphia would usually drum up significant hype. But with a three-game lead in the standings over the Sixers and only four games left on the schedule, it would take a meltdown for Boston to cede second place. Celtics coach Joe Mazzulla will need to rest his rotation players at some point. The teams at the top of the standings often do, at the expense of dropping a few games to close out the year. It doesn’t sound like he has any interest in…