At the end of the 10 rounds, the top four teams will go forward to semifinals and a final on neutral courses, with all previous points and games wiped.
After 10 weeks of testing matchplay, only the bottom team will not have the opportunity to become this year's winner.
St Clair and Taieri Lakes went into Saturday's sixth round tied for last place, with three points and nine games each.
Playing away from home. St Clair posted a 5-1 win over a weakened Island Park sextet which was without the services of Phil Bungard, Michael Smith and Chris Snow.
The win gave St Clair three points, leaving the Mosgiel golfers with some work to do in the final four rounds.
Meanwhile Chisholm Links posted a convincing 5-1 win over Taieri to be tied for the lead with Otago on 10 points and 18 games, although the Balmacewen team has a game in hand after having a bye on Saturday.
The stalwarts for Chisholm were Jason Pegler and Matthew Heaton, who both won their fourth games of the series.
Pegler beat Taieri's Mark Andrews on the final green on Saturday, while Heaton required 16 holes to beat Callum Stringer.
Brent Butler, Mark Collie and Peter Rae all won for Chisholm, while junior representative Hayden Robertson was the only Taieri winner, beating MacKenzie Gibson on the final green.
For St Clair Joshua Taylor, Joseph Hancock, Ross Colquhoun, Callum White and Chris Idour all won, leaving Island Park's Jarden Hammond as the only local winner.
