Johnson could barely hide his frustration after a Millennium Stadium reverse in which England failed to capitalise on a set-piece dominance that saw them spend extended periods camped in the Welsh 22.
The former Leicester lock was particularly bemused by England's failure to register a try, the first time they had failed to do so since a turgid draw at Murrayfield during the 2010 Six Nations.
But, having had time to analyse the game, Johnson believes there were plenty of encouraging signs as the red rose gear up for their World Cup opener against Argentina in less than four weeks' time.
"I was disappointed," he said. "It was a Test we threw away, but we said that when we looked at the tape we expected to find some positives and there were.
"We created plenty of opportunities, we had a lot of ball and if we had got a try in the first half it would have changed the nature of the game. They probably went in thinking they won that half with the score at 6-6.
"We missed a few things and we should have scored, we also had problems at the breakdown but you have to find these things out now in August, not in New Zealand in September.
"I wanted to win but if we had scored a pushover try and maybe won 16-6 it may have masked a few things.
"But in New Zealand people will not talk about how we played in Cardiff, they will only talk about how we play out there."
Saturday's performance was a worrying hark back to the early stages of Johnson's reign, where an inability to create saw them serve up turgid fayre.
But the emergence of the likes of Ben Youngs, Ben Foden and Chris Ashton had added a bite to England's attacking game, notably in their thrilling autumn success over Australia and a Six Nations dismantling of Italy.
Johnson insists his side are not too far away from producing that sort of rugby again as they look to get through some pre-season rustiness, and expects an improvement when England face Ireland in their final warm-up fixture on August 27.
He added: "We were disappointed and frustrated on Saturday, but this team has won a Six Nations Championship and it has won a Test in the southern hemisphere.
"We know there are areas we can get better at but we are not going to throw out all the good things we have done. There is a lot we can be better at and Dublin is another chance to get things right.
"You always try to get better, but the true test is under World Cup conditions. A game in August does not compare. We feel we can be very good and give any side a game and next time we want to be a better side in Dublin than we were in Cardiff."
England are in the midst of a week off ahead of their trip to Dublin, with Johnson set to reveal his final 30-man World Cup squad on Monday.
The England supremo is confident the likes of Lewis Moody, Youngs, Andrew Sheridan and Ashton will all be fit to face Ireland and travel to New Zealand and has challenged his side to get back on track at the scene of one of their biggest recent setbacks.
The trip to the Aviva Stadium in March saw the visitors in contention for a Grand Slam, but they were dismantled 24-8.
Johnson said: "It's a big game. We want to go to Dublin and perform because we did not do ourselves justice in March.
"For Ireland we will have narrowed things down a bit in the terms of how we want to play. We will go there and look to win.
"If you look at other teams Ireland have lost two (warm-up) games, Wales have won one and lost one, with these games you have a bigger picture in mind, but we want to get in next week and improve."
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