Celtic League: Week 17: Sunday, March 6Leinster 12 Ospreys 16, DonnybrookScorers: Leinster: Tries: Christian Warner, Shane Jennings; Con: David HolwellOspreys: Try: Jason Spice; Con: Matthew Jones; Pens: Shaun Connor 2, Jones
Both Gordon D'Arcy and Keith Gleeson made their returns from injury against the Ospreys - with the latter ending a spell of seven months on the sidelines with ankle trouble - however, neither could prevent Lyn Jones' Ospreys from taking the points.
The Welsh side moved 12 points clear of second-placed Munster at the top, despite a late surge from Declan Kidney's side.
Spice's try, added to two Shaun Connor penalties and another five points from the boot of Wales Under-21 Matthew Jones handed the visitors the spoils - but not without a fight.
With substitute prop Emmett Byrne in the sin-bin for preventing a quick release, Leinster piled on the pressure late on and got in for their second try through captain Shane Jennings after Christian Warner's first-half effort had left them 5-3 up at the break.
D'Arcy - who injured a hamstring injury in Ireland's Six Nations win over Italy last month - played an hour and sparked the Leinster backline into action late in the first half.
The home side endured a fretful opening as the elusive Spice had a fifth-minute try ruled out for a foot in touch and fly-half Connor kicked just one of three penalty shots.
His seventh-minute slot from 40 metres was the game's only score until first-half injury-time.
A Guy Easterby hack-through created havoc in the Welsh defence and with Kieran Lewis drawing his man in, centre Warner had enough pace to outdo Richard Pugh for the corner, and his third try in two matches.
David Holwell dinked the conversion wide and was made to pay after 57 minutes as Connor - having missed his fourth attempt early in the second half - made amends for a 6-5 lead.
The Ospreys were beginning to dominate and a blindside snipe nine minutes later saw the Leinster defence at sea.
With Dave Tiueti and captain Barry Williams picking-and-driving to good effect, Spice got the touchdown from a close-in ruck.
Youngster Jones tagged on the conversion and added an easy 73rd-minute penalty, with Byrne banished to the bin.
A searing Warner break allowed Jennings set up a grandstand finish but Holwell's touchline conversion mattered little in the end as the Ospreys held on for their 13th and probably most crucial win of the campaign.
(15) Gordon D'Arcy
Replacements used: Keith Gleeson and Emmett Byrne for D'Arcy and Nebbett (both 59), Aidan McCullen and Jamie Heaslip for Gissing and Costello (both 68), Gavin Hickie and Brian O'Riordan for Blaney and Easterby (both 73), Nebbett for Jennings (77-82). Not used: John Hearty
Ospreys: Stefan Terblanche; Dave Tiueti, Andrew Bishop, Elvis Seveali'i, Richard Mustoe; Shaun Connor, Jason Spice; Duncan Jones, Barry Williams (Capt), Andrew Millward, Andy Newman, Lyndon Bateman, Jonathan Thomas, Richard Pugh, James Bater.Replacements used: Adrian Durston for Seveali'i (28-35 mins), Matthew Jones for Connor (60), Richard Rees and Cai Griffiths for Spice and D Jones (both 71), Nathan Bonner-Evans for Thomas (79), Richard Hibbard for Williams (80). Not used: Alun Wyn-Jones.
Sin-bin: Emmett Byrne (Leinster) (72 mins)HT: Leinster 5 Ospreys 3; Attendance: 3,500Referee: Andy Ireland (Scotland)