Jonathan Williams faces three months on the sidelines after the Crystal Palace midfielder broke his leg playing for Wales' Under-21 side in Armenia.
The 18-year-old was replaced by Elliott Chamberlain in the 72nd minute in Wales' Uefa Under-21 Championship qualifying goalless draw in Yerevan.
"It is very sad news," admitted Palace assistant manager Lennie Lawrence.
Williams was rushed to hospital but did not need surgery and has flown back to the United Kingdom with his team-mates.
The highly-rated teenager, who graduated from the Selhurst Park academy, has made 13 Palace appearances since making his league debut against Coventry in August.
He scored his first professional goal in Palace's Carling Cup win over Premier League side Wigan Athletic in September.
Williams is yet to make his Wales senior debut but was in the squad for their Euro 2012 qualifiers with Bulgaria and Switzerland and was on the standby list for Wales' friendly against Norway last Saturday.
But Williams broke his right leg in an "innocuous challenge" winning his seventh Wales Under-21 cap in Armenia on Tuesday.
"He was obviously in a lot of pain after the injury," said Football Association of Wales liaison officer Dominic Kennedy.
"His right leg was put in a half plaster and he has flown back with the team today [on Wednesday].
"He is in good spirits and will undergo further scans when he reports back to his club."
Wales Under-21 team-mate and Macclesfield Town midfielder Elliott Hewitt said on Twitter: "Hope Palace's Jonny Williams will recover quick after a bad injury."