The Tigers lost to Craig Dagnell's second-half goal but is foucsed on an attempt to secure promotion to the top flight, but he could not hide his disappointment with his side's lack of cutting edge in attack.
"We have 18 games left in the Championship now without any distractions, but it's always disappointing to go out of the Cup," Bruce said.
"If you get a favourable draw before you know it you can be in with a chance.
"In the first half I thought we played well enough, but unfortunately we missed two or three really good chances, and that's been our Achilles heel.
"We had several opportunities and Barnsley just had the one, but they took it."