New manager Ralph Hasenhuttl bemoaned Southampton’s defending after losing his first game at Cardiff.
Callum Paterson capitalised on Jannik Vestergaard’s dreadful 74th-minute mistake to give Cardiff a 1-0 victory and move the Bluebirds up to 14th in the Premier League.
Saints, who have won only once this season, are now five points adrift of Cardiff and drop one place to 19th.
“At this level you cannot give the ball away twice in that manner,” Hasenhuttl said of the defining moment of a scruffy game.
“It is very hard to accept that we didn’t get a point, but with these mistakes we don’t deserve it.
“After half-time was the best period of the game for us.
“We had a lot of pressure and we were good with the ball, but we played too much from deep and inside instead of penetrating them.
“We need more forward runs in the coming months and less mistakes in the defence.”
Hasenhuttl, the former RB Leipzig manager, took over on Thursday after Mark Hughes had been sacked earlier in the week.
The Austrian faces a difficult start to life in the Premier League with Arsenal, Manchester City and Chelsea among his next five opponents.
“Confidence comes with good results and 1-0 here is not a good result,” Hasenhuttl said.
“We should prepare them. They have to believe in what we’re doing and I saw they did that for a very long time.
“It will be perfect if we get some results for the self-confidence. We didn’t here, but we have to keep working and they will come.
“I was not disappointed with what my team showed me, but that’s the basics. The rest will come in the next weeks.”
Cardiff have now won four of their last five home games after being written off by many at the start of the season.
The Bluebirds were again indebted to Paterson, the makeshift striker who plays right-back for Scotland, after his fourth goal of the season.
“You only have to look at the statistics for the lad, he can do anything and play in any position,” said Cardiff manager Neil Warnock.
“In the old days, we used to talk about players running through brick walls. If I asked him to do that he probably would.
“On another day we probably would have scored two or three goals, but it was not to be.”
Warnock also reserved praise for referee Jon Moss, who played a crucial advantage in the build-up to Paterson’s goal.
Cardiff midfielder Victor Camarasa had been fouled by his fellow Spaniard Oriol Romeu near the halfway line, but Moss allowed the game to continue.
“You know me, I’m sometimes critical of referees,” Warnock said.
“But I have to pay credit to Jon Moss. I don’t think any other ref would have played that advantage for us for the goal. It was a fantastic decision and I’ve got to say a big thank you.
“It’s great to be sat here now with another three points.”
