From what I can tell, this definitely is a botched rip rather than an LOD model. Mario's sideburns are colored correctly on the Referee's model while here they got mistakenly marked as his skin, and on top of that there's also some faces on the overalls that are supposed to be marked as his shirt that were correct on Golf's rip but not on this one.
This was also done back before rules were made regarding keeping the original textures intact from what I can tell, seeing as the individual textures got grouped together into a single atlas with mixed resolutions...
I wanna figure out a way to dump the models from this game in a better quality some day if I can. While the Golf models ARE fairly similar, the Tennis models were updated in a few ways such as utilizing vertex welding among other touch-ups like Mario and Luigi having textured mouths.

I get the impression that this is a LOD model that was dumped from memory during gameplay since unlike Golf, the camera in Tennis is dynamic (especially during replays) and can actually be quite far away from the characters. I imagine the high poly model is either identical to or slightly tweaked from Mario Golf's Mario, which is already on the site.

70shi, of course it does

wtf is this

This model is horrendous! Even Smash 64 and SM64 Mario models look better than this.

@Mimimax: The person who ripped this put all textures into one image, also Mario doesn't even have a texture for his body in this game and is instead colored with some material properties.

"Mamma mia!"

I like this model but his face and M logo textures are mapped incorrectly and his sideburns' textures aren't in the proper color. Should be like the referee model posted here for example. Also it would be nice to have this and the other N64 Mario games' models with all of the facial expressions (only SM64 and Smash have them all currently).