Cameron Johnson (Restricted Free Agent)
Cam Johnson, like Grant Williams, saw quite a bit of success in his third year in the league and proved himself to be one of the NBA's best distance shooters. If any one of the first three players on this list has a chance to enter the Spurs' starting lineup at some point in the future, it's Johnson, who had a serious case to be named the NBA's Sixth Man of the Year this past season. Johnson's floor spacing, length, and high basketball IQ make him a near-perfect match with the Spurs' system, particularly given the team's need for a bit more quality long-term depth at the 3.
What primarily makes Johnson an interesting sleeper candidate for the Spurs next offseason is the Phoenix Suns' cap situation moving forward, particularly now that the team is locked into Deandre Ayton's 4-year, $133 million contract. To keep their young core of Ayton, Johnson, Devin Booker, and Mikal Bridges together, the Suns will likely either be forced to sacrifice quite a bit of roster depth or go into the luxury tax.
I think there's a strong possibility that Robert Sarver is comfortable going into the luxury tax and that we see the Suns give Johnson an extension before the deadline this coming October. But in the off chance that the Suns decide to drag out his extension into restricted free agency as they did with Ayton, there could be a chance that the Spurs make an offer that the Suns aren't comfortable with matching.