Argentina\'s former tennis world number three David Nalbandian announced on Tuesday he was retiring because of a persistent problem with his right shoulder. The 31-year-old -- whose most prestigious victory was in coming from two sets down to beat Roger Federer in the 2005 Masters final -- will play a final exhibition match against Rafael Nadal on November 23 in Buenos Aires. \"It is a difficult day for me,\" said Nalbandian, who has slipped to 231st in the world rankings after another injury-affected season. \"It is a sad day but my (right) shoulder simply can\'t cope any more at the highest level.\"Nalbandian, who was world number three in 2006, won 11 ATP titles and reached the 2002 Wimbledon final when an unknown 20-year-old, but lost to Australian Lleyton Hewitt. Nalbandian, Argentina-born but of Armenian-Italian ancestry, also inspired Argentina to three Davis Cup finals, although they lost all three.    Nalbandian, who in an interview with French newspaper L\'Equipe a few years ago said he would also like to compete in the Rally World Championship, started the year well enough reaching the final in Sao Paulo where he lost to Nadal but then his shoulder problem intervened and an operation did not improve the situation. Source: AFP