The Keas won the top-of-the-table clash 26-10, a result that sees them move two points ahead of the Knights.
Linwood have won the competition in seven of the last nine seasons and have played in every final.
They are now unbeaten in their last five games after a slightly wobbly start to the season, which saw them suffer a draw and a loss inside their opening four games.
The result was revenge for Riccarton’s 32-24 win over the Keas in round four.
Hornby Panthers and Halswell Hornets also picked up wins over Greymouth Greyhounds and Eastern Eagles respectively, with Hornby leapfrogging Eastern into fourth place.
This weekend sees Linwood visit Halswell looking to consolidate their position at the top and stave off the Hornets, who are also challenging for top spot.
Riccarton make the trip over the Alps to take on the Greyhounds at Wingham Park, who have picked up just one win all season, beating Eastern in round seven.
Eastern host Hornby in Saturday’s other match, and the Eagles will be hoping to regain fourth place after slipping out of the playoff spots with their loss to Halswell.
