Buenos Aires, Argentina ? Juan Martin del Potro dispatched Nikolay Davydenko, 6-1, 6-4, 6-2, in their Davis Cup semifinal Friday to put Argentina one win from avenging its loss to Russia in the 2006 final. The 19-year-old del Potro gave Argentina a 2-0 lead after seventh-ranked David Nalbandian beat Russian Igor Andreev, 7-6 (5), 6-2, 6-4, in the first singles match.