After copping a headbut which forced Porter to the canvas, the 31-year-old's support staff decided to throw in the towel in the second of four rounds.

In controversial circumastances, referee Gary Dean didn't call it a clear knockdown for Quinlan, leaving Porter to fend for himself from the floor.

The bout, televised as an undercard to the Anthony Mundine vs Robert Medley fight, was Porter's first time back in the ring after four years in retirement.

Monday's bout at the Sydney Entertainment Centre was Porter's sixth professional fight.

He has now won three of his six by knockout, with the two prior to Monday’s lost narrowly on split points.

Previously as an amateur Porter fought 55 times and amazingly lost just one of those.

While no fight has been scheduled, it is believed Porter is still interested in boxing professionally on a part-time basis.

He currently works at the University of New England.