Tries from Jonathan Davies, Gareth Davies and Josh Turnbull looked to have given the Welsh region a comfortable win against their nearest challengers for the RaboDirect Pro12’s final European spot.
But handling errors and woeful defending late in the match allowed the Galwegians back in to the match in a rollercoaster final 20 minutes as the impressive Fionn Carr and Robbie Henshaw.
Wales centre Jonathan Davies got the Scarlets off the to the perfect start in Llanelli as the home side set about a game of running rugby at a sun-drenched Parc y Scarlets.
A quick tap from scrum-half Gareth Davies, saw Rhys Priestland play a superb ball over the head of opposite number Dan Parks doing his usual best to avoid collisions in the 13 channel.
Jon Davies fed youngster Jordan Williams to break down the left wing and, with options available either side, he played his team-mate on his inside for the Wales centre to run in unopposed. Priestland added the conversion.
Connacht got on the scoreboard four minutes later when the Scarlets were penalised, Parks making no mistake with the attempt at goal.
Priestland then spurned what looked like an easy effort as his penalty attempt drifted wide of the left upright and Parks reduced the Scarlets’ lead to one point mid-way through the first half with his second penalty of the match, but the Wales outside-half made up for his early effort with as his second attempt from distance on 24 minutes stayed straight to bisect the posts.
Almost immediately from the restart, great hands from forwards John Barclay and Jake Ball in the breakdown presented a steal to send the Pro12’s leading try-scorer Gareth Davies away on a break, but he couldn’t quite find Jon Davies running an inside line.
Priestland missed his second penalty of the first half after an excellent drive from the Scarlets forwards destroyed the Connacht scrum against the head, his effort again drifting left to bounce back off the left upright.
The Scarlets forwards again dominated at the breakdown and when Connacht were penalised, Priestland made good with another kick from distance with six minutes of the half remaining.
Parks passed rather than go aerial and more good work at the breakdown saw another penalty to the Scarlets, but Priestland missed again as he saw a central kick skew on to the right upright and bounce away and the home side were relatively happy with a 13-6 lead at the break, but the real drama was still to come.
Another great attacking move from the Scarlets saw the ball run through the hands and played out wide, but replacement lock Richard Kelly was held up short as he dived for the line.
After several resets at the attacking scrum, Gareth Davies fed Kristian Phillips who sent Jon Davies towards the tackle-shy Parks to get over the gain line metres from the Connacht tryline and Gareth Davies sneaked in under the posts for his ninth league try of the campaign; Priestland adding the conversion.
The ever-impressive Liam Williams then inspired the try of the match as he collected a kick forward by Robbie Henshaw on his own tryline and the full-back fed Priestland in the Scarlets 22 with the outside-half running towards the right flank to draw defenders.
A pass to Phillips allowed the winger to storm upfield through the disorganised Connacht defence before handing off to flanker Josh Turnbull who had the legs to run in unopposed from the half-way line. Priestland’s conversion attempt skewed right.
With Gareth Davies down injured before going off with a dead leg, his opposite number Kieron Marmion exploited space with a quick tap to drive through Jordan Williams and Ken Owens for Connacht’s first try of the match on 55 minuites, the TMO confirming the score.
Parks failed to get the draw on his conversion from wide right, but the signs were there that the Irish side were growing in confidence going forward on a fast track.
A good kick-chase from O’Halloran saw Rhodri Williams concede a scrum five on the hour mark, but the Scarlets forwards produced another devastating drive against the head to win the penalty and allow Priestland to clear to half-way.
Another Scarlets chance as they went in search of the bonus point came to nothing as Parks missed a tackle on Phillips and the winger motored toward the Connacht tryline, but his offload outside went into touch.
The home side were again guilty of throwing away the chance of a try-scoring bonus point away as Jon Davies played in Phillips who would have been clear on the left wing, but Phillips fumbled the catch forward.
Connacht came close to scoring their second try with 10 minutes left, but after the forwards ran through the phases on the left, the ball was moved right and replacement Darragh Leader was tackled into to touch with the tryline in touching distance by Jordan Williams on right wing.
The respite for the Scarlets was temporary as replacement outside-half Miah Nikora put in a deft cross-field kick for Carr to catch and dot down.
Nikora added a difficult conversion from wide left to bring the score to 25-18 and a potential losing bonus points for the Irish side.
A lack of pressure from the Scarlets from a long kick forward by Priestland allowed Carr time to idle up from his 22 before breaking as he stepped past flanker Barclay. Swift’s pass outside allowed Henshaw to burst through a cover tackle from Jon Davies to dot down in the corner.
Nikora’s conversion didn’t have the distance, keeping the Scarlets 25-23 in front with less than four minutes left on the clock.
With tension rising in the Parc y Scarlets, the home side finally secured the try bonus point in the final minute as replacement centre Gareth Maule found his way over to touch down on the line, the TMO confirming the try was good and Priestland added an easy conversion to strip Connacht of their losing bonus point.
In a final twist in the match with the clock red, more poor defending from the Scarlets allowed Henshaw to step inside and feed number 8 Eoin McKeon who ran in down the right and behind the posts to restore their losing bonus point and ensure they head back to Galway with a second bonus point as reward for their four-try haul.
On what could have been an impressive day out after their early dominance, Simon Easterby’s side will be disappointed to have given up two points from a comfortable position, but their five points gained consolidated their sixth place with the gap to Connacht now seven points with four games remaining.
MORE: The latest football news
MORE: The latest tennis news
BIOGRAPHY: Marcus Rashford