Based on my experience and observation the actually effect seems to be to move the player HALF a block.
So red arrows on a DMC would be Visually thus:
x M x M x TO x M x M x
- - - - - ....... - - D - -
x x D x x ..... x x x x x
I agree. I use blue arrows on my left and right DC as well, and it seems to be very effective at stopping flank attacks from AMR/AML. And it certainly reduces (but does not eliminate) the number of times that they end up far forward on attack.
I have also been told that it is not useless to put blue arrows on defenders and red arrows on strikers:
Blue arrows on DC - Apparently you can keep DCs from advancing and getting caught out, but they also wont go out to block the long shots.
Red arrows on ST - Apparently you can keep STs up in the box with a more attacking mentality.
I have been trying putting blue arrows on my left and right DC and leaving my middle DC with no arrows to test this. I consistently have the best GA in almost every season that there are no token buyers in my league.
I've never really tried using red arrows on strikers
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