Jamie Delgado has replaced Alan Mackin in Great Britain's Davis Cup team for the Euro-African Zone relegation clash against Ukraine in Odessa.
Delgado lost close matches in the doubles and singles against Israel
Mackin's success in a Challenger event in France this week meant his schedule was too tight to join up with the team for the vital clash.
GB captain John Lloyd Lloyd said: "Alan would have been faced with a quick transition onto a different surface.
"As Jamie was already out here it made sense to bring him in."
Delgado, who will join up with Andy Murray, Greg Rusedski and Jamie Baker, played in GB's defeat by Israel at Eastbourne in July.
He has yet to win a Davis Cup rubber in five attempts.