The Ospreys claimed a narrow 23-16 PRO12 victory over Cardiff Blues at the Millennium Stadium on Saturday.
The win moves them back into the play-off positions. In an entertaining opening period, the Liberty Stadium-based team took a 20-10 half-time lead through tries from James King and Jonathan Spratt, while Dan Biggar added 10 more with the boot.
Leigh Halfpenny scored all of Cardiff's points before the interval and added two more penalties in the second half, but Biggar's three-pointer confirmed a crucial result.
Despite having nothing to play for, the Blues had the chance to spoil the Ospreys' chances of qualifying for the top-four.
After the Scarlets' 28-20 victory over the Newport Gwent Dragons earlier in the day, the onus was on Steve Tandy's men to secure a win which would keep them in the hunt.
But they didn't get off to the most auspicious of starts when Six Nations player of the tournament Halfpenny scampered over.
However, the Swansea outfit gradually got into their stride and, after Biggar had reduced the arrears with a penalty, a fine move was finished off by King.
Although Cardiff's full-back briefly levelled the scores with a three-pointer, the Ospreys regained that advantage through the boot of their stand-off before Spratt touched down after excellent work from Justin Tipuric and Richard Fussell.
The play-off contenders were in control at the break, leading by 10 points, but successive Halfpenny penalties in the second half quickly put the game in the balance once again.
It was what the Blues deserved after fighting back, but Tandy's side simply piled further pressure on Cardiff's line and Biggar sealed the win with another from the tee.
For Cardiff Blues:
Pens: Halfpenny 3
Tries: King, Spratt
Cons: Biggar 2
Pens: Biggar 3
Cardiff Blues: 15 Leigh Halfpenny, 14 Owen Williams, 13 Gavin Evans (c), 12 Dafydd Hewitt,11 Harry Robinson, 10 Rhys Patchell, 9 Lloyd Williams, 8 Luke Hamilton, 7 Sam Warburton, 6 Michael Paterson, 5 Lou Reed, 4 Filo Paulo , 3 Scott Andrews, 2 Marc Breeze, 1 Sam Hobbs.
Replacements: 16 Kristian Dacey, 17 Thomas Davies, 18 Taufa'ao Filise, 19 Robin Copeland, 20 Rory Watts-Jones, 21 Lewis Jones ,22 Ceri Sweeney, 23 Gareth Davies.
Ospreys: 15 Richard Fussell, 14 Tom Habberfield, 13 Jonathan Spratt, 12 Ashley Beck, 11 Tom Isaacs, 10 Dan Biggar, 9 Kahn Fotuali'i, 8 Jonathan Thomas, 7 Justin Tipuric, 6 James King, 5 Ian Evans, 4 Alun Wyn Jones (c), 3 Adam Jones, 2 Richard Hibbard, 1 Ryan Bevington
Replacements: 16 Scott Baldwin, 17 Duncan Jones, 18 Dmitri Arhip, 19 Lloyd Peers, 20 Joe Bearman, 21 Rhys Webb, 22 Matthew Morgan, 23 Ben John
Venue: Millennium Stadium
Referee: Nigel Owens (WRU)
Assistant referees: Ian Davies, Wayne Davies (WRU)
TMO: Nigel Whitehouse (WRU)