Argentina have taken a big step towards reaching the Davis Cup tennis final after David Nalbandian and Juan Martin Del Potro secured a 2-nil lead over holders Serbia on the opening day in Belgrade.
The home team's hopes of advancing to their second successive final suffered a huge blow before a ball was hit as world number one Novak Djokovic pulled out of the opening singles rubber with pain in his lower back and ribs.
Djokovic, who won the U.S. Open in New York this week, arrived in Serbia less than 24 hours before his scheduled tie with Nalbandian and could not recuperate in time.
Replacement Viktor Troicki was beaten in 4 sets, while Del Potro produced a clinical performance to beat Janko Tipsarevic in straight sets to put the 2008 finalists in the driving seat.
In the other semi-final in Cordoba, Spain also holds a 2-nil lead over France with David Ferrer and Rafael Nadal both scoring straight sets wins over Gilles Simon and Richard Gasquet respectively.