NBA 2K18 save files are nothing short of an epic fail from developer 2K Sports. Not only do the save files take up an insane 5GB, they now appear to be corrupted as well.
Players are reporting corrupt save files that cannot be opened or fixed. 2K Sports has acknowledged the issue and are working on a patch.
Both Switch and PS4/Xbox One versions of the game seem to be affected, although the other consoles don’t have as big of a problem with the massive save file size.
See also: A more in-depth comparison of NBA 2K18 on Switch vs PS4
It appears that 2K Sports needs a bit more time to get familiar with the Switch programming environment.
And they might need some assistance from Nintendo, because one NBA 2K18 save file is almost as big as Super Mario Odyssey.