Croatia have omitted top player Marin Cilic from the Davis Cup side to take on Britain next week, as they have not heard from him since reports he had failed a drug test.
Press reports that Cilic had failed a drugs test at an ATP tournament in Munich in April emerged last month and the International Tennis Federation (ITF) said it would investigate the case.
Cilic has not played since he withdrew from his second round match at Wimbledon saying he was bothered by a knee injury.
He would normally have been an automatic choice for the Crotia team to take on Britain in a playoff which sees the winners play in the Davis Cup World Group next year and the losers drop into the second tier.
But instead, the Croatian Tennis Federation (CTF) announced a weakened team consisting of Ivan Dodig (world No.38), Antonio Veic (187th), Mate Pavic (370th) and Borna Coric (600th).
The British team for the September 13-15 tie at Umag, Croatia, will be led by reigning US Open and Wimbledon champion Andy Murray, currently the world number three.
"We have received nothing official on this (Cilic) case from the International Tennis Federation and as long as we have no information we cannot make any comment on it," said CTF spokesman Igor Rajkovic.
"We have had no contact with Cilic. In fact even for us he cannot be contacted."
The Croats will also have to do without another top player, Ivo Karlovic, who announced last year that he would no longer play for his country in the Davis Cup.
Croatia last won the Davis Cup in 2005 and last year Cilic and Karlovic lost 4-1 in the quarter-finals of the World Group to Argentina.