It was ninth v second at Parc Llwyn Ty Gwyn, but the battling home side emerged triumphant 9-0 thanks to three long-range goals from Williams. The win moved the Athletic on to 27 points, well clear of the relegation zone.
With league leaders Tonmawr on SWALEC Cup duty there was a chance for the chasing pack to close the gap on them at the top, but not only did their nearest rivals Whitland fail, but so too did third placed Corus.
They were rocked at home by Narberth, who emerged with a 24-15 victory. A Simon Evans try and Scott Robinson penalty and conversion gave the hosts a 10-3 half-time lead.
But Narberth hit back in the second half with three tries from Simon Griffiths, Chris Scarf and Gareth Jones. Craig Jones was faultless with the boot for the visitors and added three conversions and a penalty.
Elsewhere in the division a basement battle took place at the Brewery Field where Bridgend held on to claim a 27-20 win over Cwmllynfell. Jim Morgan and Chris O'Conner scored tries for the visitors but The Ravens hit back with tries through Mark David, Matthew Davies, Chris Alan-Purcell and Luke Roberts to seal a crucial bonus-point win.