Problems with Motion Tracking

[mirmar8]

Hi. I'm having trouble with motion tracking in VS x8. I'm trying to track motion of my son playing soccer so there are mutliple players on the field. The tracker quickly veers off my son to other players even when my son doesn't pass behind another player. I'm willing to do the tracking manually but I'm not sure how to do that. I've looked at the user manual and online tutorials I found but still can't figure it out. On one or two clips the track motion has worked fairly well. Any tips would be appreciated!

Thanks.

Martin