The would be under instruction from the clubs medical team(maybe both club doctors when a very serious injury). That said they should be prompt when called to enter the pitch and have their basic equipment close to hand ready to go so O2, defib, cervical collars, stretcher, frac-splits minimum. Just out of interest what grounds would an ambulance unit not be able to drive on to the pitch if needed. There's little as nervy as watching a group of volunteer medics struggling to carry a loaded stretcher with the injured taped in to head blocks etc the length of a pitch to the ambulance!!
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