No injury history. This is his first year as a full time defensive player. If you check my post linked above there is a bit of his history. He's from Accra Ghana in Africa and had never played football until last season when he played on special teams almost exclusively.
BYU has a very strong track program, and has a pipeline to Africa through Frank Fredricks (former Olympic runner and silver medalist a couple of times) and a couple of other guys, specifically another olympian named Leonard Myles-Mills. Frankie actually was my wife's "boyfriend" of sorts at BYU.... and I was so jealous when he sent her a postcard from the Olympics in Barcelona while he was setting records and was officially the second fastest man in the world in the 100 and 200. Grrr.... but I won her over.

Leonard was I believe putting up numbers that made him the third or fourth fastest man in the world at that time.
Ziggy came to BYU as part of the track program that seeks out African runners that want to come to BYU and train (many come due to the high elevation, incredible facilities, and top-notch coaching of Ed Eyestone who was a world class runner and is a world class guy by the way, and others). Ziggy came to school here, and still had some time left on his student visa/eligibility and is HUGE so he decided one day to come out for football. He didn't even know how to put on a uniform or how the game was played but the other players loved his enthusiasm and the coaches loved his raw talent (you can't train a guy to be that big and fast). He got put on the scout team 2 years ago, and then due to other guys getting injured he basically played gunner for a while last year. This year he got a chance due to another player getting injured and the amazing speed he had at picking up the game. Bronco Mendenhall has been great for him. For those who don't know... Bronco is BYU's head coach and was known for having quite a bit to do with Urlacher's success at New Mexico by developing the "Lobo Back" position for him and letting him develop into a dominant player. He can find talent and use it effectively for sure.
Zig is 6'6" 270-ish (and gaining) and runs a 21 second 200. That's world class speed. I've seen him do some insane stuff (like literally leaping over guys and sacking the QB).
I've also seen him run track and it is downright scary that a guy built like Clemons runs like Usain Bolt. I'm dead serious. He is like if Bolt took roids for a year and grew into a DE. He's going to be in the NFL and it's going to be awesome to watch.