Disappointed there is no Jerebko. I thought he was very good for the team last year.
Don't worry. They didn't sign him to a 5M contract to sit on the bench.
Early indications by both Stevens and JJ himself are that he will be playing more as a 'big 3' this year.
He came into the league as an SF and did reasonably well in defending James in the playoffs (yeah - a purely relative statement, of course). And given glut of 4/5s on this roster, it makes sense to try him there. I don't think he'd be put on some of the really quick 3s, but he's a good defensive option for the 'big 3s' like Lebron, Durant, Chandler Parsons, etc.
He won't have to be a play-creating 3, ala Paul Pierce, if he's on the floor with Isaiah. But he can definitely create space with his shooting and also cut and roll from the outside. He's also a nice pick & pop option with IT.