The game is not just about three points and local pride but the future of Cardiff boss Malky MacKay is also in the balance.
Cardiff are just above the drop zone but have found scoring hard at this level with just eight goals in nine matches. Swansea are favourites to take the points down the M4. Yet Mackay who could do with a win, looks increasingly likely to leave Cardiff City as his relationship with owner Vincent Tan grows ever more fraught according to the Sunday Mirror.
The manager has almost no contact with Tan and club sources told the paper and that matters are expected to come to a head very soon - especially if Cardiff lose sunday's derby clash.
Despite Mackay’s overwhelming popularity with supporters and a statement giving him his backing only last month, Tan could even dismiss the Scot if Cardiff lose heavily today.
Mackay’s lucrative contract - which does not expire until summer 2016 - is at the centre of an impasse between manager and owner.
Mackay will be due a hefty payout if he is dismissed almost three years before his deal ends. When Tan replaced Mackay’s friend and head of recruitment Iain Moody with 23-year-old Alisher Apsalyamov, there were suggestions Mackay might resign.
But the Mirror understands his contract has a lengthy notice period, meaning Mackay could end up owing Cardiff money if he walks out without good reason.
The compensation structure in his contract has been an issue - Everton showed an interest in Mackay before appointing Roberto Martinez but were led to believe the buyout figure was not far off £3million.
Tan is examining his massive investment in the club. Last week, he announced he would be writing off nearly £6million in interest owed to him on loans he has made.
In the last set of accounts - for the year ending May 2012 - Tan had already made over £37million worth of loans to the club.