Limit open 3-point shots for the Celtics
This one may sound simple, but at 36.7 attempts a game, the Celtics take the fourth most threes per game in the league. With those attempts, they are making 13 threes per game, which is good for third in the league.
In contrast, the Utah Jazz are tied for third in the NBA at only allowing 27.6 3-point attempts per game.
Like I said, it sounds too simple, but if you can force the Boston Celtics out of their comfort zone by limiting the amount of threes they take and forcing them inside the perimeter. Once they get into the perimeter, good to finishing around the basket with Rudy Gobert protecting the paint. All that this leaves teams is floaters just outside the paint, or the mid-range pull-up.
Those are the best shots that the Jazz can hope for the Celtics to take, but even then, you have to contest everything with this Celtics team. With capable shooters like Jayson Tatum, the Celtics have a team that can score off of whatever the defense gives them. This will need to be an elite defensive night for the Jazz. Forcing them off the three-point line would be a good start.