Boss Lee Carsley admits his England Under-21s suffered a “wake-up call” after their record unbeaten run ended.
The Young Lions suffered a first qualifying defeat in 11 years following a 2-1 loss to Slovenia in Huddersfield.
It was the first time they had been beaten in qualification for 55 games – since losing 2-1 to Belgium in November 2011 – after Djed Spence’s early own goal and Mark Zabukovnik’s header.
Cameron Archer pulled a goal back in injury time but the Young Lions, who have already reached Euro 2023 by winning Group G, were deservedly beaten.
Carsley said: “We were slow, lethargic, our tempo wasn’t great. Hopefully it’s a bit of a wake-up call that we’ve still got a lot of improving to do as a squad.
“They’ve had a hard, long season. We’ve been in camp for two weeks, we’d already qualified and we were just off it.
“If you play at 95 per cent at this level you will get found out. We didn’t do the basics well enough. We’ve got to learn from that. It leaves a little bit of a sour taste in my mouth.
“You have to turn it into a positive. We’ve spoken about responding to setbacks. If they’re going to have prolonged careers, they’ll have lots of ups and downs. It’s important that we learn.”
Slovenia have won four points off England during qualifying after a 2-2 draw earlier in the campaign, where they came from 2-0 behind.
They continued to be the scourge of the Young Lions when Spence glanced Luka Ticic’s free-kick into his own net after just 54 seconds.
From then it was an uphill battle with the hosts struggling to find the momentum which had seen them win their previous three games this month.
Jacob Ramsey steered their best first-half chance wide but the hosts failed to improve after the break and fell further behind after 64 minutes.
Ticic again did the damage from a free-kick and Zabukovnik crashed in a header from 10 yards.
Aston Villa’s Archer grabbed a consolation in injury time – his fourth goal in a week – but it did not stop the Young Lions slipping to a first home qualification defeat since 2010.
Carsley added: “I wanted to talk about how great they’ve been over the campaign and especially this window. Maybe it was a game too far.
“It doesn’t feel like it could be beneficial at the minute but I’ve told them we have to learn from this.
“We cannot play at 90 per cent because you’re second best and against a good well-organised team, you’re going to lose.
“We huffed and puffed. If we’d drawn 2-2 I would’ve felt the same – it was flat.”