The 22-year-old outside back couldn't remember much of the last encounter five weeks ago after he was knocked off course while chasing a bomb and his head was inadvertently kneed by teammate Andrew Everingham.
On Friday, he scored an early try, but was placed on report for a dangerous tackle on opposing winger Sisa Waqa.
That incident also came from a high kick, as Waqa landed head first after tumbling over Farrell's shoulders, although there appeared little the Rabbitohs' winger could do to avoid contact.
Eight minutes into Friday's game, a fully conscious Farrell provided a moment he'll have no trouble remembering.
He charged onto a perfectly timed pass from halfback Adam Reynolds to sprint over the line for Souths' first try.
From that point on, Melbourne were in catch-up mode, sliding to a 14-0 deficit by halftime.
Farrell also made a more positive defensive mark, when he combined with the other Dylan - Walker - to hold up Waqa.
The video referees ruled there was insufficient evidence to award a try, as a fired-up Souths defended with a manic intensity in the first half.
Farrell and Walker enjoyed better fortune than in last week's loss, when each butchered a try, the former through a fumble and the latter through a push.
The Souths' fans can rest their vocal chords for a week, as their team advance to a preliminary final for the second straight year.
Melbourne will continue their campaign for back-to-back titles with a sudden-death clash against the winner of the Canterbury-Newcastle match.