Leinster’s hopes of reaching the play-offs of the Guinness Pro12 were all but extinguished for the first time since their inception in the 2009-10 season after the Dragons completed a first ever league double over the back-to-back champions with

a 25-22 win at Rodney Parade.

It means Leinster must beat the reigning European champions Toulon in Marseilles in the semi-finals of the European Champions Cup next Sunday to keep their season alive.

Bonus-point wins for the top four of Glasgow, Munster, Ulster and the Ospreys had left Leinster nine points off the pace and thus having to win yesterday, but it was not to be.

Leinster have finished in the top two and earned a home semi-final in each of the five years since the play-offs were introduced.

Indeed, they have not finished outside the top three since ending up in eighth place in the 2003-04 season, which makes this their worst league campaign in 11 years.

Ben Te’o was the saint and sinner, scoring two fine tries either side of one by Jimmy Gopperth to turn an 8-3 deficit into a 22-8 lead. But a try by James Dixon precipitated a yellow card for Te’o, and in his absence James Benjamin scored two tries for the Dragons.

With three rounds of matches remaining, Leinster sit eight points behind fourth place. Hence, even if they won their last three games away to Ulster, at home to Treviso and away to Edinburgh, it is now highly unlikely that the team who have played in the last five finals will take their place in the semis.

Yesterday’s defeat was their seventh of the league season, their worst record in four seasons.

Even if they were to win their remaining fixtures, that would be three wins off their previous lowest victory total of 15; last season and the season before they won 17, and it was 18 in the season prior to that.

Toulon warmed up for Sunday’s semi-final with a 35-24 win away to Grenoble on Saturday, with Matt Giteau and Bryan Habana returning from injury to score a try apiece and Leigh Halfpenny kicking five from five for a 13-point haul on his first appearance since suffering concussion playing for Wales on the final day of the Six Nations in Rome.

Meanwhile, Munster number eight James Coughlan will play in the Top 14 next season after Pau, coached by the former Munster assistant coach Simon Mannix, clinched the ProD2 title and, with it, the sole automatic promotion place courtesy of a 31-5 win over Montauban. Sean Dougall is also bound for Pau next season.