Unscrew the nut that connects the drain to the flange using an adjustable wrench if you are replacing the pop-up drain. Then remove the drain flange from the T-connector.

If you can't unscrew the drain flange from the T-connector, use a reciprocating saw with a metal-cutting blade and cut the drain assembly away just above the T-connector.

The concrete slab stress of the pressed flange decreases with the increment of time. But the diminished stress value decreases with the increment of the shear connector rigidity.