Home advantage gives them a chance - you can never write them off in front of their marvellous supporters - but there is no doubt in coach Ian Morgan's mind about the enormity of the task his side faces.
" It's easily the biggest game Barnhall have ever played. We're in fourth place and within reach of the first division and our aim is to get there. Obviously it's going to be a very tense finish with four sides in contention for that last spot and dropping points at this stage is going to be crucial."
"Harlequins are a fabulous side but I don't for one minute think we can't beat them. We'll need a near perfect performance to do it and that's what we'll aim for and see what happens."
" They put over 50 points on Bohs last time but we beat Bohs at a time that changed our season around."
Morgan is referring to a time back in December when Barnhall travelled to Limerick after a couple of surprise defeats and came away with the points and new spring in their step.
"Yeh, things could have gone either way then. I think if we'd lost that one we'd have struggled. But fair play to the lads, it was them who turned things around."
Morgan also points to the return to Parsonstown of it's favourite son, Trevor Brennan, "He's been brilliant all along for us, on and off the pitch. I think he's playing the best rugby of his career right now. A huge influence on everyone around him."
Barnhall wind up their campaign with games against Midleton (away) and Old Crescent (home). Beating Harlequins today is a tall order and though not beyond them, the very basic requirement is that they dont lose by any sort of margin.