Any number of things. Could have fainted, had blurry vision, tripped over the sidewalk, bowling ball fell out of a window, etc.
The terminology "freaky thing" seems to indicate that it was an actual one time occurrence that happened (bowling ball, iron bar) but it wouldn't be the first time that Cappy was inarticulate so I wouldn't put too much weight in his words. It may actually be a medical situation beyond an actual accident.
This^. Cappy has the communication skills of a farm animal and that may be an insult to all farm animals.
He likely has not chosen his words carefully in trying to be vague about describing the situation, so his utterances can lead to a wide range of speculation.
I have considered all of the possibilities already stated on this thread but "freaky thing" and "a situation developed" do not leave you with much, and added together let the mind wander.
Double vision, syncope (fainting), irregular heartbeat are things that are measurable. What I do note is that Pelech was never removed to the hospital by ambulance as most emergencies are, as far as we we know. There is a team doctor in house, so it was dealt with and stabilized on site.
I ave thought of two other possibilities that a rational speaker could call "freaky thing" or fit into "situation developed" and that is he may have swallowed his tongue, which is a popular description of a seizure but really doesn't happen the way it sounds. You can't swallow your tongue but a seizure can create a type of retraction that blocks the air passageway temporarily. So seizure is the thought.
Another is an equipment failure and "injury" from a pre-game warming up, such as a stationary bike. Players sometimes use the bike to warm up before going out, and it could have collapsed under him (liability matter).
The amount of time that has passed without releasing a diagnosis or description is what is "freaky" and is on the part of the organization.
We don't need to know, but we would like to know.