Wales manager John Toshack says he was pleased to see his players' disappointment at the 1-0 England loss.
"It's a defeat at the end of the day, and, given that, to see how bitterly disappointed the team are is encouraging," Toshack told BBC Sport.
"That was a real education for our youngsters against one of the top six sides in the world.
"It was a poor goal but we came back. Our passing in their half let us down, we couldn't get on the end of things."
Toshack says everything had gone according to plan in the first half, increasing his frustration at Joe Cole's deflected 53rd-minute strike.
"Wales goalkeeper Danny Coyne made a great first-half save from Wayne Rooney, but apart from that they didn't have too many chances," said Toshack.
"If Paul Robinson hadn't denied John Hartson it could have been different.
"Conceding early in the second half was exactly what we didn't need.
"We finished strongly and the plan had been to come back at them in the last 20 minutes, but it didn't go our way."
Toshack will lose John Hartson to suspension for Wednesday's game in Poland after the Celtic striker received his second booking of the campaign.
"We knew the danger going into this game because we had eight players on yellow cards, but we couldn't think about Warsaw," said Toshack.
"Craig Bellamy will also be out with his injury, so it means there will be opportunities for others up front."
West Brom striker Rob Earnshaw impressed after coming on for the final 20 minutes against England, and he will be expected to start against Poland.