Spain head coach Luis Enrique admits there will be further checks on Sergio Reguilon after the Tottenham defender was substituted at half-time during the friendly match against Portugal on Wednesday.
The left-back started the match in Lisbon but with withdrawn at the interval after picking up an unspecified knock in the first half.
Speaking after the game, Enrique said the national team doctors would have to examine the Spurs full-back before issuing any concrete update.
"It is a blow that the doctors have to see," he told EFE Noticias.
"I hope it doesn't get complicated."
Reguilon joined Tottenham from Real Madrid in the summer transfer window, signing a five-year contract at the Tottenham Hotspur Stadium.
There was interest from Manchester United, but Spurs moved quickly to sign the 23-year-old for an undisclosed fee, with Real inserting a reported £27.5million buy-back clause.
The Spain international impressed on loan at Sevilla last season, helping them win the Europa League as well as securing a fourth placed finish in La Liga.
Tottenham host London rivals West Ham after the international break, and Spurs boss Jose Mourinho will be keen to have Reguilon available as the north London side look to build on their 6-1 victory over Manchester United.
