Damian Lillard
After seeing how last year's roster flaws came back to bite them, it was clear that the Bucks needed a defensive-minded guard to pair with Damian Lillard. While he almost certainly will not start alongside Lillard in the backcourt, Delon Wright will make for a great substitute off of the bench to pair with the All-Star guard to patch this hole.
When Wright and Lillard are sharing the floor, the latter will have a weight taken off of his shoulders because he'll be able to focus more on defense. Of course, he'll still have some responsibility on that end, but having a 6-foot-5, ever-versatile combo guard next to him to take on the tough defensive assignments will certainly help ease the workload.
As a combo guard, Wright can also handle the basketball quite a bit. That means he could allow Lillard to play off-ball at times or fill in for him entirely while the star catches his breath on the bench. Again, it all goes back to the angle of versatility, as Wright's presence will allow the Milwaukee Bucks to mix things up quite a bit, especially in the backcourt.
Lillard and Wright will more than likely get well-acquainted during their time together in Milwaukee.