Ralph Hasenhüttl believes lessons will be learned from his first match in charge after Southampton were beaten 1-0 by Cardiff City in south Wales.
Saints improved after the interval, but shot themselves in the foot when Callum Paterson capitalised on a defensive error to break the deadlock 16 minutes from time.
It proved the decisive moment, securing a fourth successive home win for the Bluebirds.
“Today I thought we could take one point, and in the second half I thought we could win the game, because it was our best period,” Hasenhüttl said.
“We were improving our performance and getting better chances. For that, it was a pity we gave it away so easily with two horrible mistakes. At this level, you can’t do that because you can’t win.
“I said to my guys ‘we don’t lose a match – either we win or we learn’. Today we learned that passion and good character is basic – I think we had that today, but it’s not enough.”
Hasenhüttl has only had two training sessions with his new team since his appointment as manager, but identified signs of progress.
“I wasn’t disappointed about the parts of the game we tried to improve over the past two days – it was ok,” he added.
“I saw a lot of things we have been training – very aggressive pressing, but it was clear there is a lot of work to do here.
“We have to improve our deep running behind the defence. We did that too seldom today, therefore we didn’t force them to make the mistakes we made.”