Getting Hightower back is arguably New England's biggest off-season move. Hightower is the Patriots' quarterback on defense, and the depth behind him is thin.
He has also literally saved New England's two most recent Super Bowl victories from going the other way. He stopped Marshawn Lynch at the one-yard line in Super Bowl XLIX to set up the Malcolm Butler interception, and he strip-sacked Matt Ryan in Super Bowl LI, which led to the Patriots making it a one-score game at the time.
The only big thing the Patriots have to figure out now is what to do with Malcolm Butler.