Lonnie Walker IV needs to play consistently well on offense
As you can see in some of Walker's highlights, it should go without saying that he's more than capable of having some explosive performances on the offensive end of the floor. There's increasing evidence that suggests that he can become a reliable three-level scorer that can also hold his own on defense.
Unfortunately for Walker, though, that potential won't matter much if he isn't able to remain consistent. White has managed to become one of the league's best two-way guards in the past couple of seasons and, even if he isn't always the biggest stat-stuffer on offense, he generally makes good decisions and is a valuable asset on defense.
While Walker can make a 31-point, 6-rebound game look easy, on other occasions he's more or less disappeared. With a reliable guard like White on the roster, that will be a surefire way for Walker to find himself on the bench.
On the other hand, if Walker can rebiably score, grab a few rebounds per game, share the ball, and play even decent defense, he'll stand a much better chance of competing for the starting spot. Assuming he gets more touches and is given more consistent playing time this coming season, seeing more consistent output from him is well within the realm of possibility.