Mumbles jumped three points clear of the bottom and are now level with Felinfoel who they beat 26-16 at home. Basement club Seven Sisters are now four points adrift though came close Corus before eventually being edged out 20-14.
The chasing pack in Division Three West also benefited from the top team's involvement in the cup as Trimsaran, Llanelli Wanderers and Llangefni all closed the gap on Penclawdd.
Trimsaran moved to within two points with a 43-12 win over Pembroke Dock Quins, Llanelli Wanderers beat Tumble 29-20 and Llangefni won 22-17 at Tenby. Hendy are still waiting for their first league win after losing their 14th game at home to Laugharne.
Bryncoch gave a rousing performance before losing 16-0 to Cwmavon who stay top of Division Three South-West, two points ahead of Nantyfyllon. However Tonna are dangerously placed in third, three points behind Cwmavon but with three games in hand after seeing off bottom side Alltwen 24-3.
Llandybie gave themselves a glimmer of hope after winning the game of the day in Division Four West, beating Fishguard 13-7 at home in the basement battle. They are now only two points behind Saturday's opponents in the league table.
Leaders Pontarddulais held onto their five-point lead at the top with a 41-22 win over Neyland who drop to fourth after Ammanford and Llandeilo won their respective games. Aberavon Green Stars pulled off the top display in Division Four South-West after holding leaders Morriston to a 16-16 draw that threw the title race wide open. Those dropped points allowed Heol y Cyw to close the gap at the top to a single point while Birchgrove are also within striking distance following their wins over Glais and Abercrave respectively.
Division Five West leaders Llanbydder won 36-5 against Gowerton while Division Five South West top side BP Llandarcy ran out emphatic 59-5 winners at home to Cwmtwrch.