In pictures: Action from ATP World Tour in Doha, Qatar

Defending champion Novak Djokovic made a sticky return to action before recovering from losing the opening four games to beat Germany's Jan-Lennard Struff at the Qatar Open on Monday.
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Serbia's Novak Djokovic serves the ball to Jan-Lennard Struff of Germany, during the ATP Qatar Open tennis competition in Doha on January 2, 2017. (Karim Jaafar/AFP/Getty Images)
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Serbia's Novak Djokovic returns the ball to Jan-Lennard Struff of Germany, during the ATP Qatar Open tennis competition in Doha on January 2, 2017. (Karim Jaafar/AFP/Getty Images)
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Serbia's Novak Djokovic serves the ball to Jan-Lennard Struff of Germany, during the ATP Qatar Open tennis competition in Doha on January 2, 2017. (Karim Jaafar/AFP/Getty Images)
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Jan-Lennard Struff of Germany serves the ball to Serbia's Novak Djokovic, during the ATP Qatar Open tennis competition in Doha on January 2, 2017. (Karim Jaafar/AFP/Getty Images)
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Jan-Lennard Struff of Germany serves the ball to Serbia's Novak Djokovic, during the ATP Qatar Open tennis competition in Doha on January 2, 2017. (Karim Jaafar/AFP/Getty Images)
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Serbia's Novak Djokovic returns the ball to Jan-Lennard Struff of Germany, during the ATP Qatar Open tennis competition in Doha on January 2, 2017. (Karim Jaafar/AFP/Getty Images)
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Belgium's David Goffin reacts during his match with Robin Haase of the Netherlands, during the ATP Qatar Open tennis competition in Doha on January 2, 2017. (Karim Jaafar/AFP/Getty Images)
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Robin Haase of the Netherlands returns the ball to Belgium's David Goffin, during the ATP Qatar Open tennis competition in Doha on January 2, 2017. (Karim Jaafar/AFP/Getty Images)