The reigning RaboDirect PRO12 champions have endured a nightmare start to the new season with three consecutive losses.
Meanwhile the Ospreys have been a polar opposite and are unbeaten and sit at the top of the league table.
Tandy admits the below-par start to the season has been hugely frustrating but he reckons his side can burst into life at Parc y Scarlets.
“It’s not time to panic, we haven’t been too far away and you don’t become a bad team over night” said Tandy.
“Our performances haven’t been up to where they should be as Ospreys but there is no bigger game than Friday night. We have licked our wounds and are ready to go down there.
“They are favourites and a side that has not lost but hopefully we can stop that winning run. The only way we will get through this is by sticking together.
“The boys thrive on games like this weekend. They are looking forward to the challenge and can’t wait to play.
“The form book goes out the window in derby matches. The Scarlets are on a high but we will go down there as party poopers.”
The Ospreys are set to welcome back Ryan Jones for the clash. The triple Grand Slam back-row forward underwent key-hole knee surgery in the summer and has yet to feature for the Ospreys. But he is in line for a place on the bench at Parc y Scarlets.
“Hopefully we will have one or two boys back. Ryan is potentially fit for the bench. It’s highly likely he will feature,” added Tandy.
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