A record crowd turned out at Parc y Scarlets, with more than 14,000 backing their Scarlets team in the 80-minute battle - creating a big rugby occasion with tensions running high both on and off the field.
Earlier in the week, Simon Easterby, the Scarlets Head Coach had said that the big derbies had a life of their own and form would not be a major factor - and while the winning Scarlets put everything into their performance, some big decisions didn't go their way and a brave home team came off second-best for the first time this season.
After winning three from four games, the Scarlets fly high up in the top of the RaboDirect Pro12 table. While that maybe no immediate consolation after a frustrating and disappointing night for Simon Easterby's team, the 18 league fixtures ahead will give the West Wales side plenty of time and scope to show their ambition and intent in this competition.
Head Coach Simon Easterby said: "It was very disappointing for us and the players are hurting right now but we have to take it on the chin and deal with it.
"They put a lot of pressure on us and competed in the breakdown and didn't get picked up for it - they certainly did a job on us. It didn't help when we went a man down but they'd had the upper hand in the scrum early on and that had a bit of an impact in the first half - but all over the field we were generally second best. They were good at scrambling when we came back at them - the truth is we just weren't as good as them on the day.
"It was a big night, plenty going on but we're not panicking, there were a few issues up front but it's not a major concern at this stage - we've shown we can compete in our opening games across the mix of our game so we'll keep cool heads after this initial disappointment.
"Our thanks to the many thousands of supporters who turned up and backed us so vocally at the game, it was great to see a full house at our home, it shows what regional rugby can offer and that's positive for the future."
Easterby said he wasn't focusing on goal-kicking as a deciding factor adding that his outside half has been striking the ball very well.
He added: "Not getting all your kicks can hurt at some stages in the season but we're working hard and Rhys is striking the ball very well - there were just some very narrow misses inches away and off the posts. You can't react irrationally to things like that - we're only four games in and we're not getting overly concerned about it.
"The boys showed their resolve by coming back to secure a losing bonus point; we have done well to close out games so far this season so we'll learn from this one and it will only make the group stronger."
Easterby wasn't going to be drawn on some big decisions made from the centre including Andy Fenby's controversial disallowed try or Samson Lee's sin binning; adding that it would depend on what the referee had asked from his match officials.
"I think we may have been unlucky on a couple of decisions; but that's how it can go and we had our chances to nail a try or two later as well and didn't take them.
"We know we have to be more accurate in these big games, derbies are physical and going into Europe we have to match that. The frustration is losing when you know you haven't played as well as you could have. And that's what the boys are feeling right now."