The Blues went into the Round 18 fixture knowing victory would take them back into the top four but they fell just short against a Munster side who now top the standings by 13 points.
Leigh Halfpenny kicked all 15 points for the Blues, with Ronan O’Gara notching 11 for Munster, including the conversion of James Coughlan’s first-half try.
A losing bonus-point sees Dai Young’s men remain in fifth spot in the table but they could now be overtaken by the Scarlets who face Benetton Treviso in Llanelli on Sunday.
The Blues opened the scoring in the second minute at the Cardiff City Stdaium courtesy of a straightforward penalty from Halfpenny but it was Munster who looked the more dangerous in the early stages.
A captain’s tackle from Blues skipper Paul Tito on opposite number Mick O’Driscoll forced a penalty when Munster were just metres short after seven minutes, with Ronan O’Gara having already sent a fourth-minute penalty wide of the near post.
A scything cover tackle from Halfpenny on fellow Lion Keith Earls then stopped a threatening Munster counter attack and the Blues wing produced another strong tackle to cut down the same man as the game approached the quarter-of-an-hour mark.
This time Halfpenny’s intervention wasn’t enough to prevent the first try of the night, however, as No8 Coughlan was on hand to take Earls’ offload and power over five metres to the left of the posts.
O’Gara added the simple extras and the visitors were 7-3 to the good and full value for their lead.
Munster blew another scoring chance with a clumsy knock on after a fine break from full back Felix Jones before Halfpenny cut the deficit with a 17th-minute penalty.
But having brought themselves back to within a single point, the Blues immediately conceded a penalty at the restart and O’Gara made them pay from wide on the left. Worse was to follow for the Blues as they were reduced to 14 men when John Yapp saw yellow with 21 minutes played.
A third O’Gara penalty extended Munster’s lead to 13-6 after 25 minutes before Halfpenny narrowly missed with a long-range effort on half an hour as the Blues gradually worked their way into the game.
Replacement Blues prop Sam Hobbs and Munster hooker Damien Varley then both saw yellow for fighting with half-time just five minutes away. While both sides lost a man, it was the Blues who were awarded the penalty and Halfpenny made no mistake from just outside the 22 to narrow the gap to four points.
Having enjoyed much the better of the final third of the first half, the Blues were rewarded with another kickable penalty when Sale-bound Munster front-row Tony Buckley infringed at a ruck 30 metres out.
Halfpenny ensured the Blues took advantage with a sweetly-hit strike from the 15-metre line on the left and the hosts were back to within a point on the stroke of half-time.
The Blues started the second period as brightly as they had ended the first but they were indebted to full back Chris Czekaj for a last-ditch tackle on Johne Murphy after Munster had failed to capitalize on a three-on-two overlap just five minutes in. O’Gara then surprisingly pulled a 35-metre penalty attempt wide of the left post to ensure the former Heineken Cup and Magners League winners remained just a point clear.
With that double escape behind them, the Blues brought three Six Nations stars back into the fold, with Bradley Davies, Jamie Roberts and Dan Parks all entering the fray.
Scottish fly-half Parks made an immediate impression as he slotted a well-taken drop goal to edge the Blues back in front at 15-13 but the lead lasted just seven minutes as O’Gara kicked another penalty with 58 minutes on the clock.
The rest of the match proved a nerve wracking affair, with the Blues attempting to move the ball wide but never coming too close to threatening the Munster line.
O’Gara missed a brace of further penalties but the Blues were unable to take advantage, with an unsuccessful drop goal from Parks the closest they came to securing the match points.
The Blues now have five fixtures remaining this term but only one of those takes place on home soil when Italian newcomers Treviso are the visitors to the capital on April 21.
Young’s men face mouth-watering derbies at all three opposing Welsh regions, starting with the Ospreys next week.
The rearranged clash with the Dragons takes place on April 29 before the regular season comes to an end with what could be vital trip to the Scarlets on May 6.
The Blues’ only other fixture is against Connacht at the Sportsground on April 15, a venue where they were beaten 18-16 last season.
