Collingtree Park kept alive their chances of progressing through to the semi-finals with a battling 3-2 home victory against Brampton Heath.
Although the visitors took the opening two games, Collingtree secured games three and four with holes to spare, before Jensen Parfitt and Josh Sampson won the 18th to clinch the last match.
Staverton Park will need to beat Northants County in a winner-takes-all home match after slipping to a 4-1 away defeat to Kettering.
Although Kettering are out of contention for qualification for the last four, they won two matches with holes to spare, before showing their spirit by taking two more points on the 18th hole.
Staverton secured a crucial point in the last game, meaning current leaders Overstone will now almost certainly drop to second in the table on points difference regardless of whether Staverton or County triumph at the end of the month.