Borna Coric will undergo knee surgery, according to Croatian press.
The 19-year-old retired with a knee injury in the first round of the U.S. Open, and returned to the court for Croatia's Davis Cup semifinal a week ago only to experience further problems.
The surgery puts him in doubt for the Davis Cup final, which Croatia reached by defeating France. Argentina will travel to Croatia for the November tie.
"It's hard to predict the rehabilitation process," said Croatian captain Zelko Krajan to AFP, though adding that he would not make any decision about Coric's inclusion on the team for a few weeks.
Coric is Croatia's third-highest ranked player and the second highest on the team at No. 42 in the rankings.