PRO12 pacesetters the Scarlets were dealt a blow when they suffered a 27-26 defeat to the Ospreys at Parc y Scarlets on Saturday.
A last-minute penalty miss from Steve Shingler meant a bonus point was all Scarlets could muster against their Welsh rivals.
With Ospreys edging themselves to a one point victory, Scarlets' lead at the top of the PRO12 is just two points, having played one game more than the trailing Connacht.
The Scarlets opened the scoring ten minutes in to the game, after shipping the ball wide to find John Barclay on the right wing, who ran it home. Aled Thomas converted his first attempt at the posts.
A kicking battle between Thomas and Dan Biggar then broke out, both kicking two penalties each in the space of ten minutes.
Ospreys then levelled the scores at Parc y Scarlets, as Justin Tipuric and Josh Matavesi helped Hanno Dirksen carry the ball over following a strong scrum, with Biggar adding the extras.
Five minutes before the break Aled Davies took the Scarlets back in front, as he reached for the line after picking the ball up from a ruck just short of the try line, and Thomas converted with ease.
Jake Ball was then shown his way to the sin bin, and with Scarlets down to 14 men, Ospreys made the most of it with the last play of the half as Alun Wyn Jones touched the ball down. To finish the first half, Biggar converted from the tee to take the two Welsh sides in level at the break.
Thomas took the Scarlets in to the lead again, converting two penalties in the opening exchanges of the second half. After an exciting first half, Eli Walker finally got a try for himself after great running from tight-head prop Dmitri Arhip, and Biggar's conversion took his side in to the lead.
Biggar had the chance to extend the Ospreys' lead to four points, but the swirling wind swept his attempt wide of the uprights with less than 15 minutes left on the clock.
With the clock in the red, replacement fly-half Shingler had the chance to secure victory for the hosts, but his penalty fell victim to the harsh wind in Llanelli, and was dragged wide.
Tries: Barclay, A Davies
Cons: Thomas 2
Pens: Thomas 4
Yellow Card: Ball
Tries: Dirksen, Jones, Walker
Cons: Biggar 3
Pens: Biggar 2
Scarlets: 15 Michael Collins, 14 Steff Evans, 13 Gareth Owen, 12 Hadleigh Parkes, 11 DTH van der Merwe, 10 Aled Thomas, 9 Aled Davies, 8 Morgan Allen, 7 John Barclay, 6 Aaron Shingler, 5 Lewis Rawlins, 4 Jake Ball, 2 Ken Owens (c), 1 Rob Evans.
Replacements: 16 Emyr Phillips, 17 Phil John, 18 Rhodri Jones, 19 George Earle, 20 Jack Condy, 21 Gareth Davies, 22 Steve Shingler, 23 Regan King
Ospreys: 15 Dan Evans, 14 Hanno Dirksen, 13 Ben John, 12 Josh Matavesi, 11 Eli Walker, 10 Dan Biggar, 9 Tom Habberfield, 8 James King, 7 Justin Tipuric, 6 Dan Lydiate, 5 Alun Wyn Jones (c), 4 Lloyd Ashley, 3 Dmitri Arhip, 2 Scott Baldwin, 1 Paul James.
Replacements: 16 Sam Parry, 17 Nicky Smith, 18 Aaron Jarvis, 19 Rory Thornton, 20 Dan Baker, 21 Olly Cracknell, 22 Martin Roberts, 23 Sam Davies.
Referee: Nigel Owens (Wales)
Assistant Referees: Leighton Hodges (Wales), Wayne Davies (Wales)
TMO: Jon Mason (Wales)