Teenager Borna Coric looks likely to miss Croatia's Davis Cup final at home against Argentina in November as he prepares to undergo knee surgery.
The world number 42, who has lost three straight matches while suffering from injury, was said by Croatian media to be undergoing the procedure within days.
Coric has had to retire in two of his last three matches, including the first round of the US Open against Feliciano Lopez after playing just seven games. He lost in three sets in the Davis Cup semi-finals this month to Richard Gasquet.
"Sadly I need to undergo a surgery to solve my knee problem," Coric was quoted in Croatia's Sportske Novosti. "I will do it next week in Zagreb. "I still hope to join my team in the finals in November."
The youngster was diagnosed with both inflammation in the knee and a bone irritation, Sportske Novosti reported.
He will need two months of rehab, putting November 25-27 Davis participation in definite danger.
Croatian captain Zeljko Krajan told local media: “It is still early, I would not automatically write off Borna. "He will try his best to recover by the end of November. How all of this will flow, we don’t know, but it is hoped that all is not lost.”