A bitterly disappointed has rued Cardiff’s complacent first-half performance as the Scarlets took the spoils at the Arms Park.
The Blue and Blacks were targeting the double over their Welsh rivals after prevailing at Parc y Scarlets earlier this season
But a devastating two tries in two minutes from Johnny McNicholl and then controversially Jonathan Davies, following an earlier effort from former Cardiff scrum-half Dane Blacker, did the damage.
Cardiff trailed 19-3 after half an hour and while they battled back with tries from the ever-impressive Taulupe Faletau, Rhys Carré and Josh Adams, they left themselves too much to do as Leigh Halfpenny kept the Llanelli club out of reach.
Turnbull said: “(The Scarlets won the game) in the first half. We gave ourselves too much to do. They kicked through us, too many missed tackles, I think someone said 25 missed tackles, you can’t afford to do that, that early in the game and give them that much momentum. Then there was a little bit of lack of execution from our end through parts of the game.
“The game never really got too far away from us in the end. It’s just we gave ourselves too much to do.
“Only we can correct it. I just said in the changing room that I think in the last couple of weeks we’ve probably got a bit complacent.
“We’ve had some really good wins this year - look at Stormers, look at the Sharks game. We’ve had some good ‘W’s here, we got ourselves out of a bit of a hole when we played the Dragons away.
“But it’s important that we don’t let ourselves down by not doing the fundamentals, the things that don’t require talent. Chasing kicks hard, making the aerial contest go in our favour, which has been a strength of ours, getting the ball back in the air and a bit of indiscipline at times.
“If you are not there emotionally, it probably has a say and a show in your physicality. We’ve always said that physicality wins derbies and in the first half we weren’t physically there.
“I don’t know if we were there emotionally but these are the games you want to play in and play well in because ultimately you are testing yourself against fellow Welsh players who are vying for honours.
“If you want to kick on and put yourself in those positions then you have to turn up physically and mentally every week. We can’t become complacent and think the job is done. We have to work harder every week to get better.
“If we can get all of that back on our side, then we’ll be in a really good spot.”
Cardiff now turn attention back to the European Challenge Cup, where they sit top of Pool A, ahead of next week’s visit of Newcastle. The Falcons arrive at the Arms Park on Sunday (1pm) with tickets available now. Click here to get yours today.