IN Dublin, it's Rovers v Sligo and in Sligo it's Rovers against the Shams.
Whatever your perspective, there's no disputing the importance of tonight's Airtricity League showdown in Tallaght Stadium.
Shamrock Rovers enter this game 13 points behind the defending champions and, while two thirds of the season will remain at full-time, the reality is that Trevor Croly's men cannot afford to lose much more ground to the defending champions if they wish to reclaim the trophy.
Despite a mini-blip that put an end to their perfect start to the season, Ian Baraclough's side enter this fixture in a strong position at the top of the table.
And, after losing Jason McGuinness and Mark Quigley to the Hoops in the close season, their supporters are enjoying the struggles of the team they only know as 'The Shams' – they bristle when the Dubliners are given solitary ownership of the 'Rovers' title.
As a Tallaght native, who spent 2011 with the Bit O'Red, 2012 with his local club, and then returned to Sligo this year after new Hoops boss Croly decided against retaining him, Aaron Greene has grown to understand the local feelings in the west.
"To be fair, Gavin Peers (the Dublin -born defender) calls them 'the Shams' now, but I haven't quite got it into my head yet as I grew up around Tallaght," he laughed.
"But yeah, it's a big rivalry, and we really want to get one over on them.
"They might be 13 points adrift, but they will feel they can match us in every department.
"We know it's a huge game because, although it's early in the campaign, there wasn't too much between the teams at this stage last year. It's really important."
The 23-year-old never really showed his best form for the Hoops, with the move he craved developing into a frustrating year.
"The fairytale didn't work out," said Greene of a year marred by injuries and a loss of form that cost him his place in the side.
"It was bitterly disappointing. What can you do if you don't get selected? I wanted to do well for my hometown club and it didn't work out, but I think it's made me stronger as a person."
As a father of two young children, Jack and Lily, the 2012 return to Dublin made sense.
Now, he's sharing his time between the capital, where his family are primarily based, and the Sligo village of Riverstown, where he lives next door to Peers.
It means a lot of time on the road, but he refuses to quibble. "I'm lucky to have a job in this environment, in the way this country is at the moment," he stressed. "I'm doing it for my children's education."
Besides, football, Greene is convinced that he's in the ideal place. Right now, it's an exciting time in the west, with the Champions League looming over the horizon and a buzz around the team and town which is special to be involved in.
"There's a real sense of community," he enthused. "When you go out for lunch, you meet people selling lotto tickets for the club, or when you go out for a cup of tea, there's people coming up just wishing you to do well. It's unbelievable really.
"Money isn't flush anywhere in this country at the moment, but there'll be a huge crowd travelling up tonight, just like there was at the St Patrick's Athletic game the week before last."
That didn't end well, yet in the nicest way possible, Greene feels it might have been a necessary wake up call.
He's made an error or two in recent weeks that he wants to correct, but, overall, he's stood out this term, proving particularly effective in a central attacking role behind striker Anthony Elding.
The unavailability of Ross Gaynor and Iarflaith Davoren means he is likely to be pressed into service as emergency left-back tonight, but, in the bigger picture, he realises his versatility is a good thing and he is enjoying the managerial approach of Baraclough and his assistant Gary Stevens.
"We've got the best back-room staff in the league," he continued.
"And I feel we're getting stronger. With the team we have, we know that if we perform to our capabilities, we can win any game."
The travelling hordes would find it especially sweet if his theory was proved correct on this Dublin visit. It should be a great match.