Slovakia's Karol Beck was ruled out of the opening singles of the Davis Cup final against Croatia on Friday because of a knee injury.
The world number 57 had been selected by captain Miloslav Mecir at Thursday's draw despite not having played a match since the St Petersburg Open in October.
Beck, who was supposed to open the tie in the Sibamac Arena against Croatia's number one Ivan Ljubicic, will be replaced by the lowly-ranked Karol Kucera.
On Thursday Beck had denied failing a dope test after rumours circulated that he had given a positive test in the Davis Cup semi-final against Argentina.
The 23-year-old is still scheduled to play in Saturday's doubles with Michal Mertinak against Ljubicic and Mario Ancic, but his withdrawal from the singles is a huge blow to Mecir as he tries to land a first Davis Cup crown for Slovakia.
The news, just hours beforeplay was due to start in the Sibamac Arena, is more surprising as Beck said on Thursday his knee injury had improved significantly throughout the week.
Davis Cup rules state that the referee can sanction a change of nomination after the draw for the first or second singles rubbers if a player is "incapacitated by illness, injury, or other unavoidable hindrance".
The 31-year-old Kucera is Slovakia's most successful player in the Davis Cup having played in a record 24 ties, although he has hardly featured this year, playing just one dead rubber in the semi-final against Argentina.
His world ranking has slipped in recent years from a high of six in 1998 and he is currently languishing down at 295. He is expected to announce his retirement after the Davis Cup final.
Friday's second singles is between Slovakian number one Dominik Hrbaty and Mario Ancic.Play begins at 1830 IST.