It was not the start Scarlets wanted after finishing 14th in the URC last season.
They scored two excellent tries through Joe Roberts and Murray but paid the price for conceding three scores from driving line-outs.
“There was plenty of effort and endeavour, particularly in that first half where we looked like the team we trained to be,” said Scarlets director of rugby Nigel Davies.
“We need to see more of those moments. Some errors started to creep into our game, particularly in the second half.
“Cardiff took their tries well, but didn’t have to work hard for them. It was more about our mistakes, and we gave them three entries into the 22 where they scored.”
Scarlets were missing injured key trio Sam Costelow, Taine Plumtree and Fletcher Anderson, with 20-year-old forwards Will Evans and Osian Williams making their first league starts.
“We had a team strong enough to go and win,” said Davies.
“We’ve exposed young players and in the main they did well and will be better for this, we’ve got quality to come back.”
Positives include the defensive effort of captain Josh Macleod, who made 28 tackles, and Murray’s running threat.
Eddie James impressed as an inside centre, rather than the outside centre position where he has been played by Wales.
“Eddie’s a great rugby player and the debate will go on where he should play,” said Davies.
“He can do a particular job at 12 and can also play 13. He can run hard and get gain line, but he is also a ball-player.”
