Fly-half Rhys Priestland kicked six penalties to guide the Scarlets to an 18-14 win over Glasgow on Friday.
The Scarlets had to endure a second-half Glasgow comeback but held on for victory at a rain-soaked Parc y Scarlets.
The home side, who held on to second place in the table, looked in a comfortable position at 15-0 just after the break until they conceded two tries in the space of four minutes scored by Duncan Weir and DTH van der Merwe.
But despite a late rally from Glasgow, who earned a losing bonus point, the Scarlets held on for their fifth Magners victory of the season.
The Scarlets went into the game without seven frontline players including the likes of new Wales captain Matthew Rees, Stephen Jones, David Lyons, Sean Lamont, Tavis Knoyle, Jon Davies and George North.
But the region more than held their own during a first half played out in torrential rain, with the likes of youngsters Nick Reynolds on the wing and number eight Ben Morgan stepping up.
Priestland had much the better of the conditions compared to his opposite number Ruaridh Jackson, who badly missed both his first-half penalty shots.
On the other hand Priestland found the target with four out of his five penalty attempts as Scarlets led 12-0 at half-time.
Priestland's first effort came on just seven minutes after the Scarlets went through the phases despite the wet conditions.
Thefly-half doubled the lead with a 17th-minute penalty before the Scarlets finished the half much the stronger with the Warriors full-back having a nightmare under the high ball.
Glasgow were not helped by the loss of skipper John Barclay to the sin bin after he kicked the ball out of a ruck. It allowed Priestland to put over two more penalties on 35 and 37 minutes.
The Scarlets began the second half well enough, with Priestland successful with a fifth penalty on 47 minutes to extend their lead to 15-0.
But the sin-binning of lock Lou Reed for a professional foul proved crucial as Glasgow scored two converted tries in the space of four minutes.
Not only were the Scarlets reduced to 14 men but their defence disappeared as replacement Weir skipped past two tackles for the first try.
And Glasgow got back to within one point as Max Evans broke through and put Van der Merwe over for the second try to send a bit of panic into Scarlet ranks.
But they were given some respite when Glasgow were penalised for being in front of the kicker and Priestland converted his sixth kick on 70 minutes.
Pens: Priestland 6
Tries: Weir, van der Merwe
Cons: Weir 2
Yellow cards: Barclay (Glasgow -34min); Reed (Scarlets - 51st min)
Scarlets:15 Daniel Evans, 14 Lee Williams, 13 Regan King, 12 Gareth Maule, 11 Nick Reynolds, 10 Rhys Priestland, 9 Martin Roberts, 8 Ben Morgan, 7 Rob McCusker, 6 Josh Turnbull, 5 Damian Welch, 4 Lou Reed, 3 Deacon Manu, 2 Ken Owens, 1 Iestyn Thomas.
Replacements: 16 Emyr Phillips, 17 Phil John, 18 Peter Edwards, 19 Dominic Day, 20 Richie Pugh, 21 Gareth Davies, 22 Dan Newton, 23 Scott Williams.
Glasgow: 15 Peter Horne, 14 DTH van der Merwe, 13 Max Evans, 12 Graeme Morrison, 11 Federico Aramburu, 10 Ruaridh Jackson, 9 Colin Gregor, 8 Richie Vernon, 7 John Barclay (c), 6 Robert Harley, 5 Richie Gray, 4 Aly Muldowney, 3 Ed Kalman, 2 Dougie Hall, 1 Jon Welsh.
Replacements: 16 Fergus Thomson, 17 Kevin Tkachuk, 18 Ryan Grant, 19 Tom Ryder, 20 Calum Forrester, 21 Henry Pyrgos, 22 Duncan Weir, 23 Colin Shaw.
Venue: Parc y Scarlets Referee: Peter Fitzgibbon (Ireland)
Assistant referees: James Jones (Wales), Simon Harris (Wales)
Television match official: Hugh Watkins (Wales)