The United frontman beat Lukasz Fabianski to a loose ball, prodding it ahead.
But Fabianski, realising his mistake, pulled back his arms.
Rashford nonetheless managed to dangle a leg and make contact with the Swansea keeper but was already on his way down with the ball well out of reach.
Neil Swarbrick waited and waited but then pointed to the spot, roared on by the Stretford End but leaving much of the viewing public back home stunned.
It was a dive, they chimed in near-universal agreement, with BT Sport pundit Graham Poll eventually admitting it should have been a yellow card for the England striker.
Here’s how Twitter reacted:
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