Ben Davies has warned that Ryan Giggs' youngsters must grow up fast on the international stage or Wales' Euro 2020 qualification ambitions will perish.
Wales meet Hungary in Budapest on Tuesday in a game which has taken on added importance after the weekend's Group E results.
Hungary moved to the top of the section by winning 3-1 in Azerbaijan, three points ahead of Wales – who have a game in hand – after the Dragons were beaten 2-1 by Croatia.
The youthful nature of Giggs' side was reflected by the fact that six of the starting XI have made their international bows since the Manchester United great was appointed Wales manager 17 months ago.
"This is their first real taste of international football," Tottenham defender Davies, one of the few survivors from Wales' Euro 2016 squad to start in Osijek on Saturday, said of the young players in Giggs' squad.
"But we haven't really got too much time for that learning curve if we want to qualify for the Euros.
"Sometimes it doesn't matter how you win games.
"It's just making sure that we stop the opposition from doing their thing and show a better account of ourselves."
Wales were forced to play catch-up on a scorching afternoon in Osijek, when the thermometer reached 30 degrees and players took water breaks at the halfway point of the first and second periods.
Croatia led 2-0 through a James Lawrence own goal and an Ivan Perisic strike at the start of the second half as the home side dominated courtesy of Luka Modric's midfield mastery.
But Wales fought back through substitute David Brooks' deflected drive and had late chances to snatch a draw as Giggs' side finished strongly.
"We have to start games better," Davies said.
"We can't afford to concede sloppy goals like we did. Hopefully when those chances come it's to win a game.
"I think we're a better team than we showed.
"But it's not great to play in the middle of the day in 30 degree heat. It took a lot out of us."
Wales' visit to the Groupama Arena now looks a pivotal fixture in the race for qualification.
Hungary's win against Croatia in March has generated belief they can secure a top-two spot, and victory on Tuesday would give them a six-point advantage over Wales.
"If we'd have won here it would have put us in an unbelievable position," Davies said.
"But it hasn't really changed from the first week. We've got six more games and they're all massive for us."
