The incident, in stoppage-time of United's 2-1 victory at Anfield, was missed by match officials.
Slovakia international Skrtel appeared to tread on De Gea's calf in the final seconds as Liverpool chased an equaliser.
The incident, in stoppage-time of United's 2-1 victory at Anfield, was missed by match officials.
Slovakia international Skrtel appeared to tread on De Gea's calf in the final seconds as Liverpool chased an equaliser.