While there is definitely such a thing as the 'sports casual' look, this isn't how most people go about trying to achieve it. Sports casual usually involves a smart pair of jeans, a casual jacket, and maybe a polo neck. This guy has gone for a totally different approach, and we're not sure it's one we'd ever try out ourselves. He seems to love it, though, and so our hat's off to him. Perhaps he could use it to cover up that headband.
It's the sensible shirt which really sets this look off for us. If everything he was wearing was crazy, we could just write him off as one of the many people with a crazy dress sense you'll find in any given Walmart on any given day. The shirt suggests a degree of dignity, though, which is totally at odds with the jean shorts and that tennis headgear. Tucking the shirt into the waistband of the shorts is the coup de gras.