its a gamble AT BEST, to try and use the offside trap as part of your defense. if a linemen doesnt see it, youre fucked and now have to chase down a striker. when i played club my coach would always try to play the offside trap, and id be the sole defender that was fast enough to try and chase down the striker that got through. playing the offsides does pay off because no one can get to your goal, but then again if they get through, its them vs your keeper