Regardless of how much stronger the center position is than the common narrative on its weakness would have you believe, productive fives are still the most valued commodity out there. And when you've got three when you only need two, you deal from the position of strength to concurrently fill one of your weaknesses. This is what the Nuggets intended to do this summer when they traded Koufos to the Grizzlies, receiving in exchange backup power forward Darrell Arthur and the rights to draft-and-stash big man Joffrey Lauvergne.
In theory, the Nuggets dealt an excess asset to fit a more pressing weakness. However, both of those criteria are subject to scrutiny. Importantly, the word "backup" in that description of Arthur is doing rather a lot here. Arthur is a decent player, indisputably, but he is also an average to decent backup at a position where that is not too hard to come by. Arthur helps a team on both ends of the court, but not hugely - he is a solid placeholder until the star player returns after the timeout, and not capable of much more than that.
The same is somewhat true of Koufos, a quality player, but a fringe starter in light of the aforementioned league-wide depth at the center position, and certainly only a backup in Memphis behind the reigning Defensive Player of the Year, Marc Gasol. But if you're trading a backup for a backup, you should be sure you're getting the better backup. Put simply, Koufos is better than Arthur, by a noticeable amount. This is true of both his value as a player and his value as an asset. Not only has Arthur yet to produce any season of the quality that Koufos did last year (8.0 ppg, 6.9 rpg, 1.4 bpg, 17.2 PER), but he is also one year older and with a much greater injury history. By no performance metric did Denver upgrade in this swap, and Lauvergne does not offset it. And ultimately, rather than balance their roster, they only further unbalanced it.
[...] Memphis now has one of the best centers in the league (Marc Gasol) and one of the best backup centers. And all it cost them was a highly replaceable player that they needn't even look outside to replace, given the presence of the incumbent Ed Davis. Denver, meanwhile, now has a whole at center and a glut at power forward that will be asked to mask it. And that's all they have to show for the loss of what should have been a great trade asset.