West Brom manager Steve Bruce admitted his team were sloppy as they were beaten 1-0 by League One Derby in the Carabao Cup second round at Pride Park.
Louie Sibley scored the only goal of the game in the 15th minute to send the underdogs through to the third round.
Bruce accepted he gambled by making 10 changes but insisted they had enough chances to go through, with Callum Robinson and Matt Phillips missing good opportunities before Tom Fellows skied over from 10 yards late on.
Bruce said: “When I look back now, have we done enough to win it? I’m not so sure. We knew it was a bit of a gamble from me to play as many kids and also the players who needed to play.
“It was in the back of my mind that you run that risk but I still think we created enough chances. We didn’t particularly play great but we should have been two up in the first three minutes.
“The frustration for me is that we’re sloppy, we’re not clinical enough and it niggles away at me constantly because we’ve created enough.”
Derby interim manager Liam Rosenior saw his side extend their unbeaten run to five matches in all competitions.
He said: “I couldn’t be prouder of the group, the young players that came in and showed their quality and spirit against what is an outstanding team.
“What pleased me most was the energy and commitment. We had to work really hard against some top players but what I was so impressed with was how brave they were.”
