I see them (seemingly easily) add Dots, Donuts and Other Visual Indicators around players as they move (rapidly) around the field.
The key part in "seemingly easily" is the "seemingly" part.
There are a number of ways to do tracking in AE, here is more info: After Effects Help | Tracking and stabilizing motion
Also, you may need to key out or rotoscope the players on the field to make the graphics seem more integrated. Info on rotoscoping here: After Effects Help | Managing and animating shape paths and masks and info on keying here: After Effects Help | Keying
The technology used by sports broadcasters is number one, expensive (and I mean really expensive) and number two automated and in many cases requires centers attached to the pan heads of the cameras.
It is not usable the post production workflow unless you are editing from the remote truck.
Thank you for your input!
Have you seen hudl.com — it is a service for schools that provides a process for by a video (in post) can be tagged/tracked (i.e. players) If you would be so kind to check that out and let me know if this is something different and/or if you have any thoughts on how they do that?
You can easily track in AE or lot's of other software and add a marker to a person. I'm imagining that hudl.com uses some kind of tracking software. It could be anything. All of these systems requires someone to manually select a target, track it and then apply the tracking info to the target.
Here's a very quick tutorial on adding a target to someone marching in a parade... It shows the basic steps. It's not too hard.