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If you look at that graphic from my video, Gunter and Chester are marking the same player and nobody is on Eriksen. Ampadu has every right to be where he is because he was pressing the midfielder who had the ball before that.
Allen has to sprint back because he notices nobody is on Eriksen. He was marking the other midfielder in view before that, I think it's Sisto, but decides Eriksen is more of a priority. By that time, it's too late.
Whichever way you look at it, it's really poor defending to let Eriksen have that much room. 5 players marking 3 is not good, but we will learn from that.