RHYL will be relegated from the Welsh Premier League at the end of the season if Barry Town United win promotion from the Welsh League, after a comprehensive 4-0 defeat to drop rivals Aberystwyth Town at Park Avenue.
It would be the second time the twice former champions have dropped down into the second tier, losing their place in 2010 after failing to gain the FAW domestic licence, but returning in 2013 as Cynru Alliance champions.
The first goal of Friday night's game arrived after 26 minutes when Luke Borrelli took advantage of some poor defending and fired home following a short corner.
Malcolm Melvin had the ball in the net minutes later, but his effort was flagged offside, while Toby Jones almost equalised for the Lilywhites but his shot hit the woodwork.
Two quickfire goals in the second half sealed Rhyl's fate, ex-player John Owen outmuscling the visitors' defence before buying his shot, and Borrelli then stole the ball from the Rhyl defence to add his second of the night.
And Owen rubber salt in his former club's wounds with his second of the night from a Geoff Kellaway pass six minutes from time.