Argentina named David Nalbandian and teenager Juan Martin del Potro to play in the singles in their Davis Cup world group semi-final against Russia at the weekend.
"David and Juan Martin will be the singles players," team captain Alberto Mancini told a news conference. "We haven't decided on the doubles, it depends on what happens in Friday's opening two rubbers."
"Naming them now is a lift for team morale as they don't have to live with any uncertainty about who's going to play. Everyone knows their role and that is very positive."
Agustin Calleri and Guillermo Canas complete the Argentina team for the Sept 19-21 tie.
Del Potro, 19, winner of four successive ATP tournaments this year, will be making his fourth Davis Cup appearance and his first at home.
Nalbandian warned that Russia would not struggle as much on the clay surface at the Parque Roca as other visiting teams.
"Playing on clay makes a big difference for Argentina against a lot of countries, but I don't think it will be like that against Russia," he said. "They have players who are very strong on this surface and it's going to be tough."
