Redruth boss Dave Penberthy says his players must keep check of their emotions when local rivals Launceston visit the Rec on Saturday.
The two clubs are both at the bottom of National One and fighting desperately to avoid relegation.
Penberthy told BBC Cornwall: "I don't think any game has had such significance over the years as this.
"I try and keep the players as cool as I can, but emotions run very high and I try to keep their feet on the ground."
He added: "The pressure on both clubs is massive and for the sake of Cornish rugby it's vital that both teams retain National One status."
The Reds, who are second-bottom in the table, are only above Launceston in the National One standings on account of their rivals being handed a 20-point deduction in pre-season for going into voluntary liquidation.
Penberthy said: "We've got to start winning, both clubs are desperate for points .
"I'd prefer to be in a mid-table position at this stage looking forward to the rest of the season rather than being where we are and knowing that the second-half to this season is the most important second-half we've ever had."
Redruth have not beaten Launceston in a league meeting since October 2008, and Penberthy knows it will not be easy to break that record.
"We've got to hit the ground running," he said. "You can't give a side like Launceston in a local derby here where their record is very good any chance at all so it's got to be straight from the off.
"We need to maintain our composure and our discipline has got to be absolutely spot on. We've got to maintain that for 80 minutes and play a simple game."
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