Both of Cardiff's goals came from corners where the scorers were unmarked and Barnsley manager Keith Hill insists that is the difference between his side and those at the top end.
"Everything is marginal, they are top of the league and we are near the bottom," he said.
"We have let (goalkeeper) Luke Steele down. He has made two matchwinning saves and we conceded from both corners and the players are responsible for the individual mistakes they have made.
"The individual errors cost you and that is the difference between the cream and the elite and us at this moment in time. Performance-wise there wasn't an awful lot of difference between the two sides. But that is the mentality of winning.
"It is the first time we have conceded from set-plays in a while and we have conceded two. That's what has cost us. We huffed and puffed, we could have had one or two decisions go our way, but we didn't get them. But we need to show more ruthlessness to make sure the opposition don't score."
Cardiff rose to the summit after Crystal Palace lost at Leeds and the win was their first on the road for seven games, though Malky Mackay played down the importance of ending their away-day blues.
"It was just good to have another three points, coming to a tough ground," he said.
"We were playing against a team that has a fresh influx of players through the week, so we always knew it was going to be difficult. I am delighted to come away from here having been clinical and getting the three points.
"We were quite comfortable and in the second half we started really well and on another day could have had another two or three goals had we picked them off on the counter attack."
Nugent, 19, was making his full debut and Mackay is tipping the youngster for big things.
"He is very calm and composed, from day one of pre-season he has been excellent," he said.
"He is desperate to do well and work hard and if he keeps improving eventually Cardiff will have a very good player on their hands. But he has to keep listening."