The Scots overcame a rusty start to pile the pressure on Wales in the second half in search of a first win in Cardiff since 2002, but were let down by their own errors, according to Townsend.
Wales’ first try from George North saw the hulking wing burst through the tackles of Scotland centres Alex Dunbar and Huw Jones, while the second score from centre Jonathan Davies saw the latter at fault again as he was weak in the tackle again.
It was 12 points gained for Wales that proved crucial in the final result and a clearly frustrated Townsend conceded it was not good enough from Jones in particular.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
"He put his hands up to the players in the changing room straight away," Townsend told reporters. "These were errors that were big mistakes in the game.
"I thought he attacked well but if you are defending at this level you have to put your tackles in, especially when you have guys who are world class attackers.
"Huw will put the work in after this and if he gets the opportunity again he will put these tackles in."
Adding to the frustration of Townsend was a Television Match Official call he felt went against his side when Peter Horne chased down a kick from younger brother George in the Wales in-goal area and appeared to dot it down.
But TMO Rowan Kitt from England adjudged the ball had been knocked on in the grounding.
"I thought he did (score the try). It is a hard one at the time but with his reaction and the ball being underneath his body, I did think it was going to be awarded, but obviously it wasn’t," Townsend said.
Scotland had earlier had a score from lock Jonny Gray chalked off for a double movement, though that decision was more clear-cut.
"The two tries they scored, we will look at those as defensive errors. That is 14 points. We got over the try-line on two other occasions, that is 14 more points. So we will have to improve those areas," Townsend said.
Scotland will host Fiji on Saturday before matches against South Africa and Argentina on consecutive weekends after that.
(Reporting By Nick Said; editing by Amlan Chakraborty)
