With the league leaders easing to victory, Neath and Llanelli's encounter at The Gnoll became essential to each side's title hopes.
The Welsh All-Blacks started the stronger, wing Kevin James's brace along with the metronomic kicking of Dai Langdon handing the hosts a 27-9 lead at the interval.
Second-half tries from Scarlets centres Nick Reynolds and Dan Thomas hauled their team back into contention, before wing Lee Williams increased their total to 28 points. But a try from Chris Morgans and the unfaltering boot of Dai Langdon proved enough for Neath to triumph 37-28.
Llandovery struck a vital blow in the relegation battle, springing a shock win over Cardiff at the Arms Park. The Blue and Blacks seemed in comfortable control as flanker Ellis Jenkins' brace established an 18-7 half-time lead.
But the Drovers' persistence paid off as wing Shaun Jones, second-row Lee Rees and centre Matthew Jacobs crashed over in the second period, before a touchline conversion from Howard Thomas completed the comeback for a memorable 26-25 victory.
Basement-side Glamorgan Wanderers lost ground on Llandovery as Ryan Owen's hat-trick handed Bedwas victory.
The Wanderers provided spirited resistance, running in three tries through Ceri Llewellyn, Gareth Morris and Tom Rowlands, but Owen's free-scoring form, accompanied by touchdowns for Richard Jenkins and Stuart Thomas secured a 36-30 win.
Cross Keys fly-half Steffan Jones singularly defeated Aberavon 25-21, scoring all his side's points through six penalties, a try and a conversion.
Elsewhere, Newport centre Matthew Pewtner's brace helped them to a 35-31 victory over Tonmawr.