That scenario seemed something of a distant dream when O'Shea saw his side lose their first two ties in Pool 4 but back-to-back victories over previous pool leaders Racing Metro means the miracle comeback is now well and truly on the cards.
"Doing the double against Racing Metro has given us a chance," O'Shea told Sky Sports News. "It comes down to playing an incredible side like Clermont. The players just cannot wait to get out there at the Stoop.
"They are such an outstanding all-round rugby team, and they will be coming full-on. We'll meet them full-on as well so it should be a great game for the group, and hopefully just a great game anyway.
"I can't wait… the guys are desperate to get out and put in a performance."
Quins held their own for much of the Round 2 encounter at the Stade Marcel Michelin, although they left it late to take a bonus point back to London courtesy of a last-gasp drop goal from former All Black fly-half Nick Evans.
Evans' intervention pre-empted a turnaround in fortunes both at home and abroad after a slow start to the season and it could prove crucial absolutely crucial when it comes to deciding who makes it through to the last eight. But O'Shea knows that Quins were still second best against Clermont first time out and a repeat would see their Heineken Cup dream extinguished far earlier than they would like.
O'Shea only sees one way of avoiding that scenario - and that is to match Clermont in attack rather than to sit back and hope for an error-ridden performance from the French.
"We're not into moral victories - it was still a loss in France. But we'd gone through a very difficult start to the season because of form, injuries and players being unavailable. We wanted to put a marker down in that game about us as a group. We felt we created a lot of opportunities. But that was a long time ago," added O'Shea.
"We'll approach this by going for it. It's the only way we can - if you try any other way against them you will die a slow death.
"I'm just going to name their backs: Sitiveni Sivivatu, Aurelien Rougerie, Napolioni Nalaga, Jean-Marcellin Buttin at full-back, Wesley Fofana in the middle of the field - it's a mouth-watering task.
"We're not hidebound by entertainment, but when it's done right then it's good to play and good to watch. For us, it's the right way to go because we have the players who are built for speed - simple as that.
"The people who come down to the Stoop on Saturday are going to witness a great game of rugby. The forecast is for it to dry up so we'll do our best to make the pitch dry and give it a good crack."