Power Forward - Keegan Murray
Personally, I think Keegan Murray is the best fit for the roster, but he can really be a stand-in for whoever you want San Antonio to draft with their lottery pick. Josh Primo is the exception because he was only 18 on draft night, but I think lottery picks should see the court from day one, and Keegan Murray has shown that he can handle the sudden transition that comes with the NBA. In his second year at Iowa, he broke out and never looked back.
He would fit well on the Spurs as a three-level scorer who could work with Keldon Johnson quite nicely. They can both hit shots from the corner and crash boards, or they could become an inside-out forward tandem that would leave defenses overwhelmed. On the defensive side of the ball, he might pass Poeltl and instantly become the second-best defender on a very solid roster. If the Spurs draft him, there is absolutely no reason for him to sit on the bench.
The fit is there. He plays a position of need and could be an impact player on an ascending team as soon as he signs his rookie contract.
Center - Deandre Ayton
Suns center Deandre Ayton will be a restricted free agent this summer, and the Spurs have the money to offer a slight overpay. He is very much a traditional center, a lot like Poeltl, but better, younger, and capable of improving a lot. He can play an anchor role in the paint and proved in the playoffs last year that he’s a lot more than just a third option behind Booker and Paul.
He fell just short of winning a ring against the Bucks last year, but with the playoffs in full swing, he may be able to climb on top this summer.
Ayton is only 23, which means he doesn’t really place the value on a trophy as much as some older players. He would probably be happy to sign with the Spurs for as much money as possible and work the organization back into contention. If the Spurs do their job in the draft, they would find the ideal power forward to play next to him, and Keldon Johnson has shown that he can add some help in the interior as well.
If you don’t like Ayton in fiesta colors, there are plenty of other options. In the draft, it’s possible the Spurs could draft Chet Holmgren, or they could add Jusuf Nurkic or another free agent big with all their cash. It should be clear that Poeltl is not a two-dimensional player who can not help push the Spurs over the top, so they should spend money to find that guy.