The Ospreys narrowed the gap on Magners League leaders Munster by securing a hard-fought 20-6 victory over the Scarlets at the Liberty Stadium on Saturday, with a fine try from returnee Mike Phillips proving the difference between the sides.
The Wales scrum-half, who had surgery on his knee ligaments in March, crossed on the hour mark for what turned out to be the winning score after the home side had trailed 6-3 at half-time.
A second try for Wales captain Ryan Jones five minutes into injury time denied the Scarlets a losing bonus point.
But though Phillips started, the Ospreys were without Shane Williams, sidelined with a shoulder problem.
The Scarlets were also without three of their big-name stars - Stephen Jones and club captain Simon Easterby (both rested) while Matthew Rees had a shoulder problem.
After a frenetic start the Scarlets opened the scoring in the third minute with a Rhys Priestland penalty after the Ospreys had erred offside.
The Scarlets doubled their lead seven minutes later with a second Priestland penalty from in front of the posts after referee Nigel Owens had to warn home lock Jonathan Thomas after tempers were lost.
The Ospreys also spurned the best try-scoring chance when Gavin Henson broke through up the left and on 30 minutes James Hook was off-target with a penalty goal shot from 30 metres away.
But five minutes later Hook found his range planting a penalty after Mark Jones and Regan King had collided trying to collect a Priestland cross-kick.
The Scarlets and Ospreys both suffered setbacks when Morgan Stoddart and Ryan Jones were both yellow-carded for not releasing the ball on the floor on 29 and 32 minutes respectively.
In first-half injury time Hook spurned a chance to level the scores, missing a penalty from close to his halfway line.
Seven minutes into the second half blood replacement Marty Holah crossed the line but the score was ruled out for a knock-on from Hook.
But on the hour mark the try stalemate was broken when Phillips skipped past two would-be tacklers to slide in by the posts for a converted try to give the Ospreys a 10-6 lead.
As the match entered its last 10 minutes Hook planted his second penalty to extend the Ospreys' advantage.
And at the death Ryan Jones went in under the posts for the second converted try.
Tries: Phillips, R Jones
Cons: Hook 2
Pens: Hook 2
Pens: Priestlend 2
Ospreys: 15 Lee Byrne, 14 Tommy Bowe, 13 Sonny Parker, 12 Gavin Henson, 11 Jonny Vaughton, 10 James Hook, 9 Mike Phillips, 8 Filo Tiatia, 7 Steve Tandy 6 Ryan Jones (c), 5 Jonathan Thomas, 4 Alun-wyn Jones, 3 Adam Jones, 2 Richard Hibbard, 1 Paul James.
Replacements: 16 Ed Shervington, 17 Cai Griffiths, 18 Ian Gough, 19 Marty Holah, 20 Jamie Nutbrown, 21 Dan Biggar, 22 Andrew Bishop.
Scarlets: 15 Morgan Stoddart, 14 Gareth Morris, 13 Regan King, 12 Jonathan Davies, 11 Mark Jones, 10 Rhys Priestland, 9 Martin Roberts, 8 David Lyons, 7 Johnathan Edwards, 6 Vernon Cooper (c), 5 Simon Maling, 4 Lou Reed, 3 Deacon Manu, 2 Mo Schwalger, 1 Phil John.
Replacements: 16 Craig Cross, 17 Ken Owens, 18 Dominic Day, 19 Josh Turnbull, 20 Dafydd Jones, 21 Gavin Cattle, 22 Ceiron Thomas.
Referee: Nigel Owens
Touch judges: Nigel Whitehouse , Alan Jenkins
Television match official: Derek Bevan