To See Them Taken/Be Taken?

I would definitely consider the second sentence to be a lot better than the first one; however, if you wanted to use an auxiliary verb here, you could also say "I saw the players getting taken off the field". Using "I saw the players taken off the field" sounds (to me, at least) as if you are seeing players who have already been taken off the field, not as if you're watching the players as they are being taken away. Using "I saw the players being/getting taken off the field" would be a better sentence if you are saw them while they were being taken off the field, as opposed to afterwards.