Nutrient impact of squeezing water out of frozen chopped spinach
One way of looking at it is that nutrient density is increased due to the removal of water. Minerals will not have been drained away at any rate.

Example from nutritiondata.self.com:

                            water content, g per 100g  Iron     vitamin A
Unprepared thawed spinach   90.2                       1.9       11725 
cooked drained              88.9                       2.0       12061


I assume more nutrients are cooked away rather than squeezed but that was the data available.