The police are on high alert. Players and coaches are on edge. The fans can't contain their excitement.
The national sport of rugby union is taking a back seat in Wales this weekend as Cardiff and Swansea collide in the Premier League for what is being billed as the country's biggest ever football derby.
For some, it will be a celebration of the remarkable rise up the English league standings of two clubs who only recently were in the pits of financial despair.
For others, the potential for the kind of crowd violence and fan hostility that has marred previous meetings between Wales' two biggest clubs is the real story ahead of Sunday's match.
Whatever the viewpoint, it should be some occasion at Cardiff City stadium.
''We all have to be careful, calm and be aware of what could happen,'' Cardiff manager Malky Mackay said. ''But it's an atmosphere that the players must embrace.''
For so long in the shadow of rugby, Welsh football has never been so buoyant.
The country has the world's most expensive player in Gareth Bale, who moved from Tottenham to Real Madrid in August for 100 million euros ($132 million), and another star in Arsenal midfielder Aaron Ramsey, who has arguably been the best player in the Premier League this season.
It also has two teams in England's lucrative top division for the first time - a scenario that couldn't have been envisaged 10 years ago.
In 2003, financially stricken Swansea was within 90 minutes of dropping out of the fourth tier and into non-league football. The team survived relegation and was saved from bankruptcy by a fan-led consortium.
Now, the Swans play one of the most eye-catching brands of football around, having blossomed in recent years under the stewardship of Roberto Martinez (now Everton manager), Brendan Rodgers (now Liverpool manager) and now Denmark great Michael Laudrup. They also won the League Cup last season for a first major trophy in the club's history.
''The rise of Swansea from nearly getting knocked out of the Football League to rising to the top half of the Premier League and winning a League Cup title is a great story,'' Swansea winger Nathan Dyer said, ''and our recent success has been amazing for the club and Welsh football.''
Cardiff has also had its financial problems. In 2006, the club was under serious threat of administration. But it has rebounded well and after knocking on the door of the Premier League for a number of seasons, the team finally achieved promotion to England's top division last season for the first time in 51 years.
But while Swansea looks like it is here to stay, trouble appears to be around the corner for Cardiff. Reports of meddling in team affairs by Malaysian owner Vincent Tan continue to hover over the capital club and have placed Mackay - one of British football's most highly rated young managers - in a sticky position.
In the past month, a close friend of Mackay, Iain Moody, was replaced as Cardiff's head of recruitment by a friend of Tan's son who has no previous football experience and was on work experience this summer painting the walls of Cardiff's stadium. The new head of recruitment, Alisher Apsalyamov from Kazakhstan, is reported to have stepped aside this week while the British government investigates his visa.
''Nothing surprises me,'' a clearly frustrated Mackay said Friday.
Both Mackay and Laudrup are getting ready for a special occasion on Sunday, but the specter of violence is never far from this match. In 1993, Swansea fans ripped up seats and threw them at Cardiff supporters in horrific scenes that led to the game being referred to as the ''Battle of Ninian Park.'' Visiting fans were banned for the next four years.
In 2009, a referee was struck by a coin during the derby and a number of fans have been arrested for public-order offenses the last two times the teams have met.
''The rivalry between Swansea and Cardiff is frightening,'' Warren Feeney, who played for both teams, told the Western Mail newspaper this week, comparing the derby to Celtic-Rangers matches in Scotland. ''I really don't think people realize how bad it is.''
A late-afternoon kickoff time could further exacerbate matters, giving fans time to drink alcohol before the match. Police officers will be deployed across Cardiff, while Swansea fans can only claim their tickets for the match if they board special buses that will have a police escort. Police call the tactic a ''bubble trip'' and use it for certain matches where violence is expected.
There'll be plenty more at stake on Sunday than simply three points.
