The former Tottenham midfielder was afforded a glorious opportunity to put Hull the ahead against Trencin in Slovakia, but he fluffed his lines and saw his 60th-minute penalty saved before somehow smashing the rebound over the crossbar from close range.
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"You'd have put the house on that Tom would score," Hull manager Bruce said. "It was easier to score.
"We've all missed penalties, 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.
"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."
However, the Hull boss was able to take some positives out of the game and spoke of his pride at the effort shown by his players so soon after returning for pre-season.
"We needed a game like this," he added. "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."
Hull welcome Trencin to the KC Stadium next Thursday keen to use home advantage in their quest for a place in the play-off round of the competition.