Novak Djokovic expects "very challenging" John Isner test

World number two Novak Djokovic has admitted that today's semi-final clash with John Isner at the BNP Paribas Open in Indian Wells will be "very challenging".

Djokovic lost 7-6 3-6 7-6 to Isner in the last four of the Californian event in 2012, and the Serb is expecting the American to push him all the way again.

"He's definitely not somebody you like to play in the big heat with such serve," Djokovic told reporters.

"It's very challenging because he doesn't miss his serve too much, so you have to kind of be able to hold your composure from the first to the last point and be ready to play three tiebreaks."

Djokovic has won four of his six career matches against Isner.