Why the Spurs should draft Jalen Duren
I'm not opposed to the Spurs selecting a center in the lottery, so long as that player projects to be as good as or better than Poeltl going forward. Duren isn't as good now, but at just 18 years old, he could have a higher ceiling than Poeltl, who's 26. Therefore, San Antonio should absolutely draft him if he's available at eight.
As for Poeltl, he'll be an unrestricted free agent after next season and is likely to command at least $15 million a year in his next contract. That might be more than the team is willing to pay for him, especially considering they discussed a deal that would've sent him to Charlotte, which suggests that they don't necessarily see him as a part of the team's core. Selecting Duren gives the Spurs options.
Overall, Duren is a talented two-way center who has the chance to be a great player in the NBA. While he doesn't address an immediate need for the Spurs, they should draft him anyway. In fact, he'd make sense as a long-term fit at center but wouldn't immediately replace Poeltl.
But with Poeltl entering the final year of his contract and with him being one of the best centers in the NBA, the Spurs could look to trade him by next year's deadline. This would ensure that they receive assets in return for him, and it keeps San Antonio from having to re-sign him to a big deal if they are unwilling to do so.
Considering the Spurs almost moved Poeltl this past trade deadline, they could look to the draft to find his eventual replacement, and Duren could be that player.