If Leinster fall tomorrow, Glasgow have nicked themselves a home Magners League semi-final with a 37-32 win at Parc y Scarlets on Friday.
The Warriors, with fly-half Dan Parks outstanding, must now hope Scottish rivals Edinburgh can do them a favour against Leinster in Dublin on Sunday after the Ospreys notched up the bonus point they needed against the Dragons.
Parks kicked 17 points, while opposite number, Wales and Lions number 10 Stephen Jones, landed 22 for the home side to write himself into the Scarlets' record books as their leading points scorer of all time.
Glasgow had gone into the game having already secured their place in the inaugural end-of-season play-offs.
But the primary target for Sean Lineen's side was a home tie at Firhill, although they needed a big favour from the Dragons against the Ospreys down the road at the Liberty Stadium for that to happen.
The visitors were over the whitewash inside four minutes, only for Hefin O'Hare's 'try' to be disallowed by referee James Jones for a forward pass late in the movement.
Instead it was the Scarlets who were first on the scoreboard with full-back Dan Evans finishing off a flowing movement by diving over in the corner after seven minutes.
The lead, though, lasted barely five minutes as a penalty from fly-half Parks was followed by a well-worked midfield move that saw wing DTH van der Merwe cross under the posts.
Parks converted, only for opposite number Jones to pull the Scarlets back with a straightforward penalty shot on 18 minutes.
When flanker Calum Forester was put through a gaping hole in midfield for the Warriors' second try - again converted by Parks - suddenly there was some daylight between the sides.
But when Scotland international Kelly Brown was sin-binned just before the break the Scarlets hit back strongly with a second Jones penalty and a well-taken try by wing Lee Williams making it 16-17 at half-time.
The free-scoring nature of the game continued straight after the restart with Jones sealing his place in Scarlets history with a superb individual try, which took him in front of seventies legend Andy Hill (2,596) as the leading points scorer.
He and Parks then swapped a couple of penalties apiece as the Scarlets moved into a 29-23 lead, only for Glasgow to hit back again with a sparkling counter-attack which saw O'Hare show great pace and vision to cross under the posts.
Park's conversion nudged Glasgow back in front and then a superb cross-field kick from the outstanding Scotland number 10 paved the way for the bonus-point try from full-back Bernardo Stortoni.
At that stage, the Warriors were set for a home draw, but down at the Liberty a fourth Ospreys try ended those hopes.
A late Jones penalty offered the Scarlets hope, but they had to be content with another losing bonus point - a sorry story of their Magners League season.
For the Scarlets:
Tries: Evans, Williams, S. Jones
Con: S. Jones
Pens: S. Jones 5
Tries: Van der Merwe, Forrester, O'Hare, Stortoni
Cons: Parks 4
Pens: Parks 3
Scarlets: 15 Daniel Evans, 14 Sean Lamont, 13 Regan King, 12 Jonathan Davies 11 Lee Williams, 10 Stephen Jones, 9 Martin Roberts, 8 David Lyons (capt), 7 Josh Turnbull, 6 Rob McCusker, 5 Dominic Day, 4 Vernon Cooper, 3 Rhys Thomas, 2 Matthew Rees, 1 Iestyn Thomas.
Replacements: 16 Phil John, 17 Ken Owens, 18 Lou Reed 19 Johnathan Edwards, 20 Tavis Knoyle, 21 Rhys Priestland, 22 Andy Fenby.
Glasgow: 15 Bernardo Stortoni, 14 DTH van der Merwe, 13 Max Evans, 12 Graeme Morrison, 11 Rob Dewey, 10 Dan Parks, 9 Chris Cusiter, 8 Johnnie Beattie, 7 Kelly Brown, 6 Calum Forrester, 5 Alastair Kellock (capt), 4 Richie Gray, 3 Moray Low, 2 Fergus Thomson, 1 Kevin Tkachuk.
Replacements: 16 Dougie Hall, 17 Ed Kalman, 18 Dan Turner, 19 James Eddie, 20 Mark McMillan, 21 Duncan Weir, 22 Hefin O'Hare.
Referee: James Jones (Wales)
Assistant Referees: David Bodilly, Huw Griffiths