rear brake caliper piston stuck

[Monyx]

frigged if I can move them back to make room for the new pads, searched and read the tips on removing reservoir cap, draining some fluid, leveraging a gap between the old pads by opening up long nose pliers of inserting then then twisting flathead screw driver. so are the old pistons, scored and stuck in there and caliper in need of rebuild? pads were evenly worn down and rear brakes work(ed) fine without undue pressure. just can't move the pistons back