The Mubadala World Tennis Championship has been another resounding success as some of the world's top players battle for supremacy. As the tournament heads for a thrilling climax, the crowds in Abu Dhabi have been entertained by some top class action. Novak Djokovic and Rafael Nadal play again on the final day again on Saturday. Djokovic faces Karen Khachanov in the third place play-of, and Nadal takes on Greek Stefanos Tsitsipas for the title. Here, in pictures, is how the tournament has unfolded so far before the conclusion gets underway.