A Ronan O'Gara penalty in the 80th minute saw Munster edge Ospreys 22-20 in a nail-biting Magners League clash at Liberty Stadium on Saturday.
The result is major blow to the Ospreys' play-off aspirations as they trail fourth-placed Cardiff by a single point with one round to play.
In his final match at the Liberty stadium before joining Perpignan, centre James Hook looked to have given the Welsh side a vital win when he converted a penalty four minutes from time.
But a yellow card to Jerry Collins and O'Gara's last minute intervention means they still sit outside the top-four with just one game left.
Although there was no score for the first 20 minutes, both sides threatened in a frenetic opening period. Munster's Keith Earls was particularly prominent and his break nearly ended in a try but the winger knocked on with the line begging.
Hook was then denied a parting try as his foot was adjudged to be in touch. However, O'Gara finally put the first points on the board in the 24th minute with a penalty.
And Tony McGahan's men stretched their lead to 10 points when back-row David Wallace barged over, O'Gara converting. Four minutes before half-time the Ospreys reduced the gap when stand-off Dan Biggar kicked a penalty.
Munster's fly-half was then on target again immediately after the break converting another three point opportunity. The Ospreys got themselves back into the match when a strong driving maul ended in lock Alun-Wyn Jones burrowing his way to the line.
Biggar added the extras and they crossed again when French referee Jerome Garces awarded a penalty try after repeated scrum infringements.
It was the first time the Welsh team had led in the game but O'Gara helped the visitors regain the advantage when he booted successive penalties.
However, Hook looked to have secured the win with a late three points before Collins was sin-binned and O'Gara made it 22-20 to Munster.
Tries: A-W. Jones, Penalty try
Cons: Biggar 2
Pens: Biggar, Hook
Pens: O'Gara 5
Yellow card: Collins (Ospreys - 79th min)
Ospreys: 15 Lee Byrne, 14 Nikki Walker, 13 Tommy Bowe, 12 James Hook, 11 Richard Fussell, 10 Dan Biggar, 9 Rhys Webb, 8 Jonathan Thomas, 7 Marty Holah, 6 Justin Tipuric, 5 Alun Wyn Jones (c), 4 Ian Gough, 3 Adam Jones, 2 Richard Hibbard, 1 Ryan Bevington.
Replacements: 16 Huw Bennett, 17 Paul James, 18 Duncan Jones, 19 Ryan Jones, 20 Jerry Collins, 21 Mike Phillips, 22 Andrew Bishop, 23 Sonny Parker.
Munster: 15 Felix Jones, 14 Doug Howlett, 13 Lifeimi Mafi, 12 Paul Warwick, 11 Keith Earls, 10 Ronan O'Gara, 9 Connor Murray, 8 James Coughlan, 7 David Wallace, 6 Donncha Ryan, 5 Donncha O'Callaghan, 4 Ian Nagle, 3 John Hayes, 2 Damien Varley, 1 Marcus Horan.
Replacements: 16 Mike Sherry, 17 Wian du Preez , 18 Tony Buckley, 19 Tommy O'Donnell, 20 Niall Ronan, 21 Peter Stringer, 22 Danny Barnes, 23 Simon Zebo.
Referee: Jerome Garces