Similar thing happened to me while playing football (soccer for americans) in the gym recreationally with bunch of friends few years back. I was sort of jogging along the center of the playground, with my eyes on the play somewhere in the corner near opposing net and then boom - i ran into someone with my side and we both ended up on the floor. Unfortunately the other person was a guy in his late 50s or so, and fell rather awkwardly and hurt himself so bad, that he stopped playing after that for quite some time.
Anyway, i tried to explain i did not see him (as i was looking in different direction that i was moving to) and the other guys said ok, ok, but i always felt they did not believe me or something and still thought i did it on purpose or whatever. Which was weird, as we used to play with each other for years till that point, and while i may have been clumsy on occasion, surely i was never nasty.