And his side are boosted by the return from injury of Wales centre Ashley Beck who is fit enough for a place on the bench.
With Alun Wyn Jones in the Wales squad to face Italy in Rome and Joe Bearman banned, Kahn Fotuali'I leads the side from the unfamiliar position of left wing.
"This is a huge game for us in terms of shaping the rest of the season," said Tandy.
"There's no margin for error after last weekend's defeat, we are realistic enough to know we need to put in a winning performance to maintain our push for the play-offs.
"With teams in the top four playing against each other this weekend, the right performance and result could see us back into the top four and with six games left it'll be in our hands.
"It's going to be tough whatever the outcome on Friday night but as coaches we have belief in this group to tough it out when they have to."
With 15 players unavailable due to international action, Tandy has seen his squad stretched but does have James King available after he was released from the Wales squad. The former Aberavon man starts in the back row alongside Morgan Allen and Sam Lewis.
Tandy added: "If you look back at last season, we bounced back from two defeats against Ulster and Glasgow at this time of the year and went on a winning run that took us right through to Dublin at the end of May.
"It's going to have to take something similar, so we'll roll up our sleeves and get stuck into the task.
"Just as last year players like Hanno Dirksen and Eli Walker came to wider attention because we were missing people on international duty, it's time for those involved to step up and follow in their footsteps."