Ronan O'Gara missed four penalties for Munster in the Magners League on Saturday as they fell 19-14 to the Ospreys at Liberty Stadium.
O'Gara, standing in as skipper for the injured Paul O'Connell, was off-target while his 20-year-old opposite number scored 14 of his side's points.
In steady rain it was sweet revenge for the Ospreys who had conceded more than 100 points to Munster in three defeats last season, and the win ended a four-match losing streak.
Munster were forced into a late and significant change to their line-up when O'Connell pulled out with a calf strain.
The Ospreys were also without their captain Ryan Jones, who had not recovered from the back problem which ruled him out of Wales' defeat to Australia. Jerry Collins led a side which included seven players who were on autumn duty with Wales, Ireland or Scotland.
The Ospreys found themselves penalised four times in the first eleven minutes but Munster failed to take advantage with O'Gara missing two shots at goal after four and six minutes.
Munster were awarded a penalty try from a scrum much to anger of the home support. O'Gara converted in front of the posts to give the visitors a 7-0 lead on 13 minutes.
The Ospreys, with their first concerted attack, got on the scoreboard with a Biggar penalty from in front of the posts.
But two minutes later they lost Alun-Wyn Jones to the sin bin for a professional foul, although O'Gara could not convert the penalty - his third miss.
Biggar also saw a long-range effort rebound off the crossbar before he kicked a 38th-minute penalty to get the Ospreys within a point, to make it 7-6 at the interval.
The Ospreys made a dramatic start to the second half when Tommy Bowe went in at the right corner for a converted try after good work from Gareth Owen and Dan Biggar, to put the Welsh side in front for the first time.
And their second attack of the half saw them have a chance to go further ahead after Munster hooker John Fogarty was sin-binned for a professional foul, but Biggar was wide with his penalty shot.
The Ospreys thought they had scored a second try but Paul James, in the opinion of the television match official, lost the ball over the line. But they made do with a 57th-minute Biggar drop-goal as they extended their lead to 16-7.
Fortune was certainly the Ospreys as they watched O'Gara miss his fourth penalty attempt after 60 minutes.
But while O'Gara was having an off day, Biggar planted his third penalty from the halfway line as the home lead went to twelve and that was followed by Munster number eight James Coughlin being yellow-carded for kicking the ball away.
Munster kept scrapping for a points and a try for replacement Nick Williams in injury-time forced the Ospreys to defend.
Pen: Biggar 3
Tries: Penalty, Williams
Con: O'Gara 2
Ospreys: 15 Gareth Owen, 14 Tommy Bowe, 13 Sonny Parker, 12 Andrew Bishop, 11 Nikki Walker, 10 Dan Biggar, 9 Liam Davies, 8 Filo Tiatia, 7 Marty Holah, 6 Jerry Collins (capt), 5 Jonathan Thomas, 4 Alun-Wyn Jones, 3 Craig Mitchell, 2 Richard Hibbard, 1 Duncan Jones.
Replacements: 16 Huw Bennett, 17 Paul James, 18 Cai Griffiths, 19 Andy Lloyd, 20 Ben Lewis, 21 Rhys Webb, 22 James Hook.
Munster: 15 Paul Warwick, 14 Doug Howlett, 13 Jean de Villiers, 12 Lifiemi Mafi, 11 Keith Earls, 10 Ronan O'Gara, 9 Tomas O'Leary, 8 James Coughlan, 7 Niall Ronan, 6 Alan Quinlan, 5 Paul O'Connell, 4 Donncha O'Callaghan, 3 John Hayes, 2 Denis Fogarty, 1 Wian du Preez.
Replacements: 16 Damien Varley, 17 Tony Buckley, 18 Donncha Ryan, 19 Mick O'Driscoll, 20 Nick Williams, 21 Peter Stringer, 22 Denis Hurley, 23 Ian Dowling.
Referee: Neil Paterson (Scotland)
Assistant referees: Hugh Watkins (Wales), Alan Jenkins (Wales)
Television match official: Tony Rowlands (Wales)
Assessor: David Herbert (Wales)