I didn't read the article, but it's a bit more complicated than that legally (civil) speaking.
First, I'd say yes, even as a "casual spotter" in the gym, if you were not paying attention or otherwise negligent, I think you could be successfully sued. This does not mean you have some absolute duty to prevent an accident, because there are inherent dangers that come with lifting weights, but if you agreed to spot someone and you weren't paying attention, I think you could be found liable.
Remember, you have no "legal duty" to provide someone with a "spot". However, once you agree and assume that responsibility, you cannot do so without taking reasonable care to perform that duty to the best of your ability. Put simply, this means that you cannot be looking at the hottie in the spandex while someone is under the bar. However, as I said, you're under no absolute duty to prevent any accidents - just to use reasonable care.
Moving onto the case in point, the scenario is a bit different than that of the casual gym spotter. The "spotter" in this case was a coach and there would be a heightened duty to enforce safe lifting practices and to be diligent with "spotting". I don't know all the facts, but I can guarantee you the case goes forward and there might be a recovery by the injured player.