Scarlets head coach Wayne Pivac admitted his teamâs Heineken Champions Cup chances had been âhurtâ by Ulster following a 25-24 home defeat.
The Scarlets â European semi-finalists last season â are facing an early exit following a third successive Pool Four loss.
Two Steff Evans tries and a late Dan Davis touchdown â plus nine points from the boots of Rhys Patchell and Dan Jones â kept them in contention, but Ulster ultimately prevailed in bonus-point fashion.
âOur defensive inaccuracy in the first half, in particular, and with the try they scored from 60 metres, we fell off some basic one on one tackles, which is unacceptable at this level,â Pivac said.
âThey played very well, but we werenât that accurate defensively on a couple of occasions, and we paid for it. Similarly, on attack, we werenât clinical enough.
âFor us, it is about improving on that performance and keep building and making sure that we get our accuracy back into our game and put teams away when we make these breaks.
âWe have got three more games in this competition, starting next week (against Ulster in Belfast), and we want to turn tonightâs result around.
âThey hurt us at home tonight and hurt our chances in this competition, so I guess we want to try and repay the debt.
âYou can look back and pull games to bits, itâs not going to change the situation we are in. It is frustrating.
âWe have got to focus on the positives out of that game and make sure we keep building on our performances, because we have still got a lot to play for this season.â
Ireland star Jacob Stockdale produced another try-scoring performance as Ulster put a huge hole in Scarletsâ European hopes.
Stockdale, whose touchdown helped Ireland beat world champions New Zealand last month, struck in the first half at Parc y Scarlets, while his fellow wing Henry Speight, centre Will Addison and number eight Marcell Coetzee also scored, with scrum-half John Cooney kicking a penalty and conversion.
It left Ulster level on points with Pool Four pace-setters Racing 92 ahead of next Fridayâs Scarlets return fixture.
Ulster backs coach and former Scarlets and Wales scrum-half Dwayne Peel said: âWe had prepared well, and we realised it was a massive game for us.
âThe Scarlets have a fantastic home record, so it was a huge challenge for us.
âBut we couldnât have asked for more. We have got some good players in our squad, and they all stood up tonight.
âIn this period in Europe, the job is sort of half done. We are delighted with the win, but we know there is going to be a backlash at our place next week.
âWe are a work in progress. We are delighted with the win, and our aim is to get better week on week.â
In the other game last night, Edinburgh secured a 31-13 win over Leicester at Murrayfield.