Tom Huddlestone's close-range miss was "easier to score" according to Bruce, after the blunder saw his side settle for a goalless draw on their European bow against Trencin.
"You'd have put the house on that Tom would score," he said.
"It was easier to score. We've all missed penalty, we've all missed big chances in front of goal, you don't intend to do it.
"But we've missed our last three or four I think so we better start practising because we're not very good at them."
Although the Tigers were favourites to win the away leg, they still have next Thursday's game at the KC Stadium to secure a place in the play-offs.
And that is enough for Bruce, who was concerned his side might not yet be match sharp so soon after their summer break.
"We needed a game like this. I was always a bit worried we'd be undercooked a bit, it was always a big ask.
"We've only been back at work two-and-a-half weeks.
"We knew it was going to be difficult whatever team you play, especially in the middle of pre-season. But overall we'll be better for this game.
"The one thing you've got to do is take your chances when they come your way. Unfortunately we haven't taken them and we had one or two really great opportunities that would have made the second leg more comfortable."
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