Blues will be aiming to back up the spectacular 28-23 win over Ulster last time out and John, who has taken charge of team affairs with Dale McIntosh, believes a back to basics approach is the way forward.
He said: "We've got everything to play for; we've restored some pride in the jersey. The boys showed what they are capable of by beating Ulster and now we need to maintain that standard of performance.
"We need to try and improve from there and see where we finish off as a result. It's crucial to finish off the season with a bit of momentum.
"The players are buoyant after the Ulster result and having senior players back on the field like Matthew Rees and Gethin Jenkins is good because they demand high standards," he added.
"Meggetland is more enclosed (than Murrayfield) with a big atmosphere. We got back to basics last week and that's what we need to do again, we need to maintain possession and keep the same approach as we did against Ulster."