With County already confirmed in the third-fourth placed play-off next week, the head coach is looking to end on a high and take third place and secure a home match in the post-season play-off.
The teams drew in Stirling on the opening weekend of the league section but since, Southern have surged to the top spots and will contest the final against Ayrshire next week, but Cairns is seeking every possible advantage for his own teams’ game next weekend.
"Knights are the only side we haven’t beaten this season, having drawn in round one, so there is a lot to play for at the Greenyards,” he said. “They have probably been the most consistent performers in the league this season and deserve their spot in the final.
“Our three wins from three puts us in a great position to fight for that home spot in the third-fourth play-off.”
Cairns will cycle his backline against Rob Chrystie’s Knights with Marcus Holden and Craig Jardine coming in, and Grant Hughes moving to number nine.
Byron Bowes, fresh from winning the varsity with St Andrews University, will be among the visitors’ substitutes.
For their last home game of the season, Southern will be led by Grant Shiells at loose-head prop and Daniel Suddon starts as second row. FOSROC Scottish Rugby Contracted Academy player Jacob Henry returns to start in the back three with Iain Sim on the right wing.