The format of the Celtic League and Celtic Cup seasonal structure was changed once more as an antedote to league games clashing with international fixtures that had stunted the rhythm of the 2003-2004 season. Rather than spreading the Celtic Cup tournament throughout the first half of the Celtic League season as had happened previously, this time around the Celtic League Championship ran first in its entirety and finished in early April. With the Championship decided and no more league matches left to play the Celtic Cup competition followed, taking place in the remaining month and a half of the 2004-2005 season.

In another change, this time to the format of the Celtic Cup competition itself, the trophy would be decided over three rather than four rounds with only eight teams participating. During the 2003-2004 season, 4 teams out of the 12 playing in the Celtic League were seeded and went straight to the quarter-finals whilst the other 8 fought it out in a first round. This time around the top 8 out of the 11 Celtic League teams (the Celtic League had been reduced to 11 teams following the disbanding of the Celtic Warriors during the summer hiatus of 2004) took part in the Celtic Cup based upon their final positions in the 2004-2005 Celtic League table; this meant that the Celtic Cup started with a straightforward quarter-final knockout. An element of seeding was still involved in this format, but rather than base it on a previous season's results or on domestic and European performance, it was easily decided by the final table's placings. Under the new format the 2004-2005 Celtic League Champions played the eighth placed team in the table, second played seventh, third played sixth and fourth played against fifth in the quarter-finals; the semi-finals were then decided by a subsequent draw.

The Ospreys dropped the Neath-Swansea prefix to their name at the start of their triumphant 2004-2005 Celtic League season in an attempt to fully embrace the qualities of regionalism that their team represented. As the borders of their area of coverage expanded with the disbanding of the Celtic Warriors, the term Ospreys created a brand in its own right and helped to broaden the appeal to the support elements within the region that were strictly more than just Neath or Swansea. Games were shared as before between the Gnoll and St Helen’s in the final season before the completion of the Liberty Stadium which the Ospreys would share with Swansea FC from the start of the 2005-2006 season.

The season began for the Ospreys as they intended it to continue; beating Munster, who considered themselves in the title race by the end of the season with their second place finish, 34-17, at St Helen’s in the Celtic League’s opening fixture. The Ospreys gained the bonus point with four tries taking the maximum points on offer in round one and Gavin Henson provided an admirable display from the boot producing four conversions and two penalties.

The Ospreys used derby matches against the other Welsh regions to useful effect during the course of their run to the Championship winning five out of the six matches before conceding to the Scarlets in the Celtic Cup at the beginning of May. Four out of the five Celtic League victories were achieved with routs of the opposition; the Ospreys racking up at least a twenty or thirty point margin over their opponents during the course of a game with only the Dragons turning the Ospreys over in one of their three defeats during the course of the season. Even in that match, the 33-29 defeat at Rodney Parade, the first for the Ospreys all season, they still managed to stay within the seven point losing bonus point cushion as their key personnel stepped up to face South Africa in the 2004 Lloyds TSB Autumn Series.

Despite Glasgow holding the Ospreys to a high-scoring 27-27 away draw it was the Irish provinces that did the best job in attempting to torpedo their title challenge. Connacht claimed the only home defeat of the Ospreys, a narrow 9-10 away victory for the Irish province, followed by Munster, who went on to beat the Ospreys home and away in the 2004-2005 Heineken Cup and who managed to beat them 13-9 at Thomond Park in mid-December in the Celtic League.

With the margins of defeat so slight, the Ospreys were able to exploit the losing bonus point in each of their three defeats adding to their seven try bonus points achieved across the course of the season. The bonus points proved crucial at the end of the season in making sure that the Ospreys were comfortably ahead of their nearest challengers. They finished with 76 points, 7 points ahead of their nearest challengers with 16 wins, 1 draw and only 3 losses. After their defeat to Munster in December, they went the entirety of the remainder of the season unbeaten, had it not been for the draw with Glasgow they would also have had a 100% record in that time.

The Ospreys picked up the Celtic League title with one match to spare defeating Edinburgh 29-12 on Saturday March 26th 2005. They could have won it with two matches to spare but were denied the opportunity of joining the success of Wales and Wales U21 on the weekend of March 18th / 19th as fellow title challengers Munster won their match against Ulster and kept themselves in the title hunt for one more week.

With the dominance of their opponents so prevalent in their Celtic League victories and even somewhat in their defeats the Ospreys were fancied by many for a Celtic League and Cup double. In the start to a Celtic Cup campaign that appeared to pick up where the title challenge finished the Ospreys brushed aside the Celtic Cup holders 23-17 at home in the final weekend of April and booked themselves a berth in the semi-finals the following weekend.

Head Coach Lyn Jones played down the Ospreys’ Celtic League form and results as they found themselves pitted away against the Scarlets in a Welsh derby semi-final. Jones’s warning had substance and two one-sided Celtic League victories for the Ospreys counted for nothing as the Scarlets embraced the one-off nature of Cup rugby and dumped the Celtic League Champions out 23-15. 0-12 down in the opening minutes of the match, 7-12 down at the break, the Scarlets clawed their way back into the match before Gavin Quinnell smashed across the line in the closing stages and, with a subsequent conversion and late Barry Davies penalty, snatched the match from an Ospreys side that had been cruising to victory.

Their run to the Celtic Cup Final aside, the Scarlets had a poor season in comparison with 2003-2004. They struggled to recapture the form of their title winning campaign as they lost the services of outside half Stephen Jones to Clermont Auvergne at the start of the season. Injuries and retirements also played their part across the course of the season; Dafydd Jones was injured on international duty during the successful RBS Six Nations campaign of 2005, and the end of the season saw the departure of the influential Stradey Park legend Scott Quinnell.

The Scarlets finished in 5th place in the league, recording just 9 wins along the way and 11 defeats. Their total of 46 points included 10 bonus points where they equalled the Ospreys’ tally of seven try bonuses and three losing bonus points. Statistically, the Scarlets’ position of fifth in mid table was deserved, conceding 446 points to the 402 that they scored. Going forward, the Scarlets punched their weight with the rest of the league, amassing a total of 48 tries, only five behind the Ospreys; it was at the defensive end that they unfortunately found parity, conceding almost as many tries as they scored; 42. Their Anglo-Welsh challenge curtain-raiser with London Wasps in August, where the 2003-2004 Celtic League Champions played the 2003-2004 Zurich Premiersip Champions, set the tone for the season as the Scarlets let a comfortable lead slip in the final stages of the match to end up on the wrong side of the eventual 17-20 scoreline.

After a promising 15-26 start away to the Borders the Scarlets' season began to unravel. In the Welsh derbies the Scarlets faired poorly, gaining only two victories all season aside from the Celtic Cup successes over the Ospreys and Dragons. They beat the Dragons and Blues comfortably at home in the latter stages of the season but prior to that it read as four straight derby defeats, including a double loss to the Ospreys. Glasgow, who the Scarlets found themselves paired with in the Heineken Cup, also added a double blow of Celtic League misery to the Scarlets with two home and away victories.

Finishing in fifth place put the Scarlets third out of all the Welsh regions and as such safely qualified for the 2005-2006 Heineken Cup. Their position in the table meant that they automatically faced the fourth place Celtic League finisher in the Celtic Cup quarter-finals; the Scarlets embraced the challenge of the Dragons with open arms. Drawn away to the Dragons at Rodney Parade, the Scarlets threw their Celtic League form away as they showed their true Celtic Cup credentials early on. A 19-49 rout of their opponents had consigned their early season defeat in the corresponding Celtic League fixture to the dustbin of history and set them up nicely for a face-off with the League Champions in the semi-final. It also represented a Celtic Cup double for the Scarlets who had dumped the Dragons out at the first hurdle in the Celtic Cup the season before.

An aforementioned semi-final against the Ospreys followed with the Scarlets clawing their way to victory after a 0-12 start before the Celtic Cup Final beckoned at Lansdowne Road. In a match where the Scarlets failed to get going, Munster more than made up for the disappointment of not being able to catch the Ospreys in the Celtic League. A Mike Phillips try and Ceiron Thomas conversion almost sparked a second half fightback for the Scarlets but they were ultimately undone by the boot of the superlative Ronan O’Gara who provided 17 of the Irish province’s points including a try in the process.

The Newport Gwent Dragons finished in fourth place behind Leinster, second out of all the Welsh regions. With 50 points and 6 bonus points, the Dragons notched 11 wins and 9 defeats, the opposite win-loss count of the Scarlets who finished a place behind them.

It was level pegging for the Dragons in the derby matches as they recorded three wins and three losses a piece. Their campaign didn’t exactly start in the best of fashions as they crashed 18-8 to the Cardiff Blues at the Arms Park, but they soon picked themselves up defeating the Scarlets 15-0 the following weekend. The Dragons were the only Welsh side to take points off the Ospreys, beating them 33-29 in their home fixture at the beginning of November.

The low point of the season came with a 55-3 away defeat to Leinster who finished just above them in the table. Kevin Morgan equalled Jamie Robinson’s Celtic League record of the 2003-2004 season scoring 12 to finish as the top try-scorer. Quarter-final defeat beckoned for the Dragons in the Celtic Cup who had worked hard to secure fourth spot only to be turned over by the Scarlets at the first hurdle.

Cardiff Blues finished bottom out of all of the Welsh regions for the second season running; ninth in total in the final Celtic League table, amassing only 40 points with 8 wins to their name, 1 draw and 11 defeats during the campaign. After a promising start to the campaign which included two wins and a draw out of four fixtures, the 11 defeats in total included a disastrous October for the region, which saw the Blues lose all four of their league fixtures during the course of the month.

Another poor run of form from November to January saw them go a further five league games without a win. It was only through a late revival, which included wins in their last two games that the Blues secured a chance at qualifying for the Heineken Cup via a play off. The ninth place finish was not good enough to qualify for the draw for the Celtic Cup and although the Blues beat Ulster, who finished in eighth place, 22-8 during the season’s final run in, their 30-14 defeat at Ravenhill in November was ultimately telling in the three points difference that existed between the two Celtic League placings.

The Ospreys' victory galvanized a very successful season for Welsh rugby; Celtic League Champions, RBS Six Nations Champions and U21 Six Nations Champions. With many of the Ospreys' key players present in the Wales Grand Slam side along with the Celtic Cup finalists the Scarlets, the dividends of regionalism appeared not only to be being paid in the regional competitions themselves but also as their Wales representatives stepped up to the international stage. It now remained to be seen if a Welsh region could retain the Celtic League trophy in the forthcoming 2005-2006 season, or if the Blues or Dragons could emulate the Ospreys’ run of the 2004-2005 season and step out from the previous season’s shadows to challenge for the Celtic League title.