Karen Khachanov and Andrey Rublev have been confirmed to play in the Mubadala World Tennis Championship which gets underway in Abu Dhabi on Thursday.
The Russian duo replace Daniil Medvedev and Gael Monfils in the men's draw after both were forced to withdraw through injury.
The 12th edition of the tournament, which takes place from Thursday to Saturday, features World numbers 1 and 2, Rafael Nadal and Novak Djokovic, as well as Maria Sharapova.
Recent ATP Tour Finals champion Stefanos Tsitipas gets proceedings underway on Thursday when he takes on Rublev from 4 o'clock.
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