But Glynneath skipper Grant Bignell said his side and fourth-placed Heol y Cyw would have a say in the final placings.
"It was a good win for us," the backrower said. "We had about 14 boys unavailable and had to call in some second-team players and some guys out of retirement. At 1.30pm, we still hadn't picked a team.
"Then our main lineout winner Gareth Howells was stomped on in the first five minutes, so he had to go to hospital for 30 stitches to his head. It got a bit ill-tempered after that, and I'm proud of the guys for digging so deep to get the win."
Glynneath wingers Tom Venn (2) and Nicky Rees were among the try-scorers, with player-coach Darren Williams running things from inside centre.
"We've won five out of nine, but we're unbeaten at home, and I think you have to look at Heol y Cyw as well. Morriston haven't won it yet."
In Division 2 West, Dunvant's exciting 17-16 win at second-placed Corus gives them a three-point lead on the table, but third- and fourth-placed Loughor (16-12 winners at home to Tonmawr) and Pontyberem (27-14 winners over Seven Sisters) are determined not to make it a two-horse race this season.
Penclawdd retain their lead in Division 3 West after a 44-5 mauling of third-placed Llanelli Wanderers - their 10th straight win - but Trimsaran are keeping the pressure on with 22-18 win at Lampeter.
Nantyffyllon retain top spot in Division 3 South-West, despite suffering a 41-0 mauling at mid-table Vardre. Third-placed Cwmavon bagged a hard-fought 24-18 win over second-placed Tonna, while bottom club Alltwen recorded their first victory of the season - a 31-21 result at home to Kenfig Hill.
Division 4 West leaders Pontarddulais retain a five-point lead at the top, despite having their match against Fishguard postponed and second-placed Ammanford winning 19-16 at Neyland.