Cardiff Blues gave Xavier Rush a winning send-off at Cardiff City Stadium, but their 13-12 defeat of Munster was not enough to prolong their involvement in this season’s Magners League. Instead, the losing bonus point secured fourth place for Munster who will travel to arch rivals Leinster in the semi-finals.

Wales and Lions centre Jamie Roberts scored the only try as the Blues extended their winning streak in all competitions to seven matches, a new record for the Welsh region.

But it was a bittersweet victory for Dai Young’s side who have finished fifth in the final Magners League table, just a point behind semi-finalists Munster.

Stand-in captain Ronan O’Gara converted four first half penalties, including three in an eleven-minute spell leading up to half-time, as Munster took a 12-10 lead into the break.

Cardiff full-back Ben Blair opened the scoring on the quarter hour mark with third attempt on goal, with Roberts muscling his way over for a converted 25th minute try.

The second half was a dour affair, with Munster having to cope with the sin-binning of prop Marcus Horan and a missed O’Gara penalty.

The deadlock was broken in the 79th minute when young winger Leigh Halfpenny stepped up to knock a long range penalty through the posts and give his side the four points, but not the semi-final spot they were battling for.

With so much riding on this game – Cardiff, Munster and Edinburgh were all chasing the fourth and final play-off place – early nerves were understandable. Passes were fumbled and wrong options taken, and Blair was off target with penalty efforts after 6 and 8 minutes.

Munster flanker Nick Williams had to be bundled into touch by Blair as the visitors enjoyed an early visit to the Blues’ 22, and the departing Xavier Rush, playing in his final home game for Cardiff, covered 30 metres on a fine break.

Rush’s run preceded Blair’s first shot at the posts but the latter opened his scoring account in the 15th minute when he punished Munster for a ruck offence.

O’Gara quickly replied for the visitors, after an offside decision, and he caught Halfpenny out with a raking kick which led to a five-metre scrum. Number 8 David Wallace attacked off the set piece, only for Martyn Williams to thwart him just metres out.

Cardiff got back on the front foot, with Ceri Sweeney and the home forwards making good yardage. A Sweeney half-break and some intelligent play from centre Casey Laulala created the space for Roberts to power through and touch down under pressure from three Munster players.

Blair tagged on the conversion from wide out, but O’Gara showed his kicking class by collecting a crucial nine points over the remainder of the first half.

O’Gara’s influence on the game shown through as he continually pushed the Blues back with some pinpoint touchfinders and well-placed returns.

Winger Tom Gleeson was perhaps fortunate to avoid further sanction for tackling Blair while he was in the air, but Munster lost a player to the sin-bin in the 52nd minute when Horan was singled out for slapping the ball out of scrum half Darren Allinson’s hands at a ruck.

The Amlin Challenge Cup finalists looked the more likely to score a try, with Ma’ama Molitika bursting forward and Sweeney also making good ground.

But Munster were able to keep their line intact and with the Blues frustrated by some lineout problems and an inability to crack the red defensive wall, the Irish side engineered some try-scoring chances.

Gleeson was close to scoring as O’Gara hung up an inviting kick, and the latter looked to have sent Springbok centre Jean de Villiers through for a try, only to be called back for a forward pass.

It was a controversial decision by the match officials, and showed just how well O’Gara and de Villiers can click with ball in hand.

It was tight and tense with mistakes at both ends of the pitch, but the 12,602 spectators present were gripped. Cardiff were next to press through Roberts, and Munster replacement James Coughlan had to be sharp to halt an attack involving Williams and Dafydd Hewitt.

Despite the best efforts of key men like Laulala, the Ulster-bound Rush and try scorer Roberts, the Blues’ search for a second try was an ultimately fruitless one.

Replacement Paul Warwick missed a drop goal attempt for Munster, and it was left to Halfpenny to decide the game, thumping a huge kick over to give the home side the lead for the third and final time.

Reflecting on what might have been, Blues boss Young said afterwards: "Well it was a win, but we didn’t play anything like we have done over the last two or three months – that’s the disappointing factor.

"We knew what Munster were going to do. Obviously they target the tackle area, they really slowed everything down there, stopped us getting any quick ball, but we caused ourselves a lot of problems.

"Our accuracy wasn’t quite there. We were untidy and lacked a lot of control in most of the things we did, things which have served us really well over the last two to three months.

"It was nice to win, but it would have been nicer – even if we hadn’t gone through (to the semi-finals) – to have won with a bit more style."