Cardiff are now out of the competition, after fielding a weakened team in the game.
It is a disappointing start to the season for the club, who have yet to score a goal in the Premier League. But their manager is unfazed.
"I think it showed that quite a lot of the lads needed games," Warnock said after the game to Sky Sports.
"You need competitive games. We had better chances than them. It [result] is disappointing.
"I more or less know what my team is going to be for Sunday [against Arsenal], and tonight didn't put me off that. Ten out of 11 players I have got in my mind.
"As I said to the lads afterwards, it shows you have got to train really hard if you are not in the team so that you take your opportunity when it comes.
"I think the depth is there. We have just got to make sure we keep the fitness levels up of the lads that are not involved, because it is such a massive step. The Premier League is 100 times more than what the Championship is in terms of movement."