I am not sure that we have a missing piece and I think that the Jazz are legitimate contenders next year. Take the current team and add Rubio and Thabo an we are already significantly better than this team and likely would have pushed the Rockets to 7 this year. I think they would have won it. That is with a Rookie back court against a Hall of fame back court. Think what would have happened if Hornacek and Russell were missing against the Rockets in 1997.
The typical improvement from rookie year to second year is significant for guards. Taking the personalities and player development of the Jazz and I expect to see greater than typical improvement from both Mitchell and Oneil. Rubio will be be like the second half Rubio or better all year. Ingles was also better in the second half of the season as he grew into his new role. Gobert will work and improve over the summer and and will play more than 50 games. Crowder will have a summer to more fully immerse himself the Jazz system I expect only minor improvement here though. Maybe a little better shot selection finishing layups. Exum will come back gang busters like he did at the beginning of last season. By the time playoffs get her he will finally be blossoming into the player we hope. He is already able to play solid defense on Harden. Incremental improvement on offense and a summer of body development as he finally begins moving up from being a kid. I really like the versatility having Favors is likely the best free agent we we will be able to get. He provides the best 1-2 center combo in the league and the ability to punish many teams with power when playing together with Gobert. In other games he can play slightly smaller line up with Thabo, Crowder, who can play stretch 4. He also provides insurance in case Gobert is injured.
AB, Neto, Udoh, Jerebko, Stockton, Tony Bradley, g-leaguers, and picks are all expendable/replaceable if the right opportunities present themselves at the same time they are decent and have good chemistry. I trust DL to manage the bottom half of the roster and potentially flip some of the bottom half into a more important contribute.