Fourteen points from the boot of fly-half Matthew Morgan helped the Ospreys defeat Leinster 19-10 in a rematch of last term's PRO12 final.
The champions battled back from a one point half-time deficit, and a ten minute period in the second half down to 14 men, to beat Leinster for their fifth straight victory in the competition.
Ospreys introduced Matthew Dwyer at hooker for his debut, and Lloyd Peers in the second-row started his first game at this level. Leinster meanwhile, made wholesale changes to their backline, with Andrew Goodman making his debut at outside centre, while Rhys Ruddock made his first appearance of the season at 6.
The Irish side were on the attack from the start, with Ian Madigan getting them on the scoreboard with a penalty goal after only four minutes. Leo Auva'a pounced on a blocked Ospreys kick to touch down for the visitors on eight minutes, with referee John Lacey needing assistance from the TMO. With Madigan adding the extras, it was 10-0.
But Ospreys came back, and three Morgan penalties made it 10-9 to Leinster at the break.
Duncan Jones saw a card after the restart, so with the extra man, Leinster turned the screw.
Sam Lewis made way for another home debutant, Marc Thomas, during Jones's absence. Morgan had spurned the opportunity to take the lead for the Ospreys, but his penalty kick just before Jones' sin-binning went wide of the posts at Liberty Stadium.
An error-strewn period saw Leinster make no headway with the extra man, and it was Eli Walker who took advantage of handling errors by the Irish side. He put the Ospreys in front before numerical parity was restored, taking advantage of a pass from Richard Fussell, who had made a great break through Leinster's defensive line. Walker did the rest, and Morgan's conversion gave the home side a 16-10 lead, as the game entered the final quarter.
Man of the match Fussell rounded off a perfect day, making his 100th appearance in the competition. Victory was secured by Morgan's drop-goal five minutes from time, to put daylight between the sides, for Ospreys' eighth consecutive win against Leinster.
Pen: Morgan 3
Ospreys: 15 Richard Fussell, 14 Hanno Dirksen, 13 Tom Isaacs, 12 Andrew Bishop, 11 Eli Walker, 10 Matthew Morgan, 9 Rhys Webb, 8 Joe Bearman, 7 Sam Lewis, 6 George Stowers, 5 Jonathan Thomas (c), 4 Lloyd Peers, 3 Joe Rees, 2 Matthew Dwyer, 1 Duncan Jones.
Replacements: 16 Arthur Ellis, 17 Marc Thomas, 18 Daniel Suter, 19 James King, 20 Morgan Allen, 21 Kahn Fotuali'i, 22 Jonathan Spratt, 23 Ross Jones.
Leinster: 15 David Kearney, 14 Andrew Conway, 13 Brendan Macken, 12 Andrew Goodman, 11 Fionn Carr, 10 Ian Madigan, 9 Isaac Boss, 8 Leo Auva'a, 7 Shane Jennings (c), 6 Rhys Ruddock, 5 Devin Toner, 4 Damian Browne, 3 Jamie Hagan, 2 Thomas Sexton, 1 Heinke van der Merwe.
Replacements: 16 James Tracy, 17 Jack McGrath, 18 Martin Moore, 19 Ben Marshall, 20 Jordi Murphy, 21 John Cooney, 22 Noel Reid, 23 Sam Coghlan-Murray.
Referee: John Lacey (Ireland)
Assistant referees: Neil Hennessy (Wales), Wayne Davies (Wales)
Television match official: Nigel Whitehouse (Wales)