Sucks for Tavares.
Hard to say when someone is milking a low blow. Most of us have been hit hard at some point in the dick/balls area, and the pain can last only a minute or much longer. That being said, Tavares is a grappler and needed the fight on the ground to win, but couldn't get it there long enough to do anything, so him trying to find a way out wouldn't be a surprise.
I would've expected a NC or a DQ in favor of myself if I was Tavares, not a DQ loss for myself since I was the person who was injured.
That loss is definitely worthy of appealing at a later date. It won't do shit for Tavares in terms of continuing in the tournament, but he might be able to get a NC, which is better for his record and potential earnings.