Owls Under-23s boss Neil Thompson was left ruing a "mad 20 minutes" after their Steel City derby defeat to Sheffield United.
A strong Blades side, featuring Paul Coutts, Martin Cranie and Daniel Lafferty, condemned Wednesday to their first loss in five matches after first half strikes from Coutts (penalty), Oliver Greaves and Martin Cranie.
The Owls, who had the better of the early skirmishes, pulled one back two minutes before the interval with a well-taken strike inside the penalty area from midfielder Liam Waldock.
But United secured the points under the lights at Hillsborough to stretch their unbeaten run to five matches.
Thompson told The Star: "It was a tough game. They had a little more experience than us. We had quite a few young ones out there.
"I thought we started quite brightly in the first 20 minutes. We created one or two good opportunities but we didn't take our chances.
"We had a mad 20-25 minutes where we conceded some really poor goals from our point of view and then we gave ourselves a mountain to climb. We gave ourselves a bit of a lifeline getting one back but it was tough work in the second half.
"We had a young-ish team and we just didn't have enough.
"It was a derby and they were a little bit older and had more nous than we did and I think you could tell that."
Thompson cut a frustrated figure post-match and bemoaned the Owls' wastefulness in front of goal.
"We have created a lot of chances this season but we just haven't taken them," he said. "The danger of that is when you don't take your opportunities, you have to keep the back door shut and we didn't do that.
"We defended very poorly.
"We have to get back on the training pitch and work hard. That's the challenge of football. There is always something that trips you up. We have had a lot of good stuff over the last two years and one or two players have moved up (to the first-team).
"When people move up out of the group - we had quite a few players missing tonight - it gives other players the opportunity. You either take your chance or you don't."
Although he was unhappy with their defending and lack of a cutting edge in the final third, Thompson praised the performance of Under-18s duo Waldock and Conor Grant.
He said: "They did really well and showed some good touches. They are only young boys so we have to tread carefully with them but they showed some promise.
"David Jones got 90 minutes which was good. He showed a great attitude throughout. I thought Jack Lee did okay, although he came off with a sore groin. I think he should be okay."