DUBAI, United Arab Emirates -- Novak Djokovic opened the defence of his Dubai Championships title with a straight sets victory over Denis Istomin, while second-seeded Juan Martin del Potro had to retire from his first-round match on Tuesday.
Top-seeded Djokovic, who is making only his second appearance this year after reaching the quarterfinals of the Australian Open, was a 6-3, 6-3 winner over 54th-ranked Istomin of Uzbekistan.
"It wasn't as easy as the scoreline indicates," said Djokovic, who has won in Dubai on four occasions. "I needed to work for my games.
"Having not played for more than four, five weeks, an official match, obviously it takes its toll on the court."
Djokovic saved all four break points he faced on serve and broke Istomin three times -- in the third and ninth games of the first set and in the second game of the second set.
Del Potro was not so fortunate, being forced to retire against Somdev Devvarman of India after losing the first-set tiebreaker 7-6 (3).
Since winning the Sydney title last month, Del Potro has been struggling with a left wrist injury that has conjured up memories of similar pain he experienced in his right wrist four years ago.
In 2010, the year after he won the U.S. Open, he played only three tournaments before and after surgery on his right wrist.
Del Potro was fighting back tears in Dubai when he came to talk to the media after his retirement.
"I don't feel really well," he said. "My wrist is hurting a lot and everybody knows what happened to me four years ago with my other wrist.
"It was really tough to play today. I tried everything. I cannot be the player I would like to be."
Having felt the pain in his left wrist during the Australian Open, Del Potro went at the end of January to consult with Dr. Richard Berger, who performed his right wrist surgery at the Mayo Clinic in Minnesota. The doctor recommended a course of physical therapy.
Asked if he would have kept playing if he won the first set, Del Potro said: "I don't think so, no. It was hurting too much."
Devvarman, a wild card who won a challenger in New Delhi last week, hit a service winner on his third set point in the tiebreaker. That proved to be the final point of the match.
"It's unfortunate, especially for a guy like him," Devvarman said. "I realized he wasn't comfortable hitting backhands and I tried to make him hit as many as I could, and he wasn't really hitting over it so I knew he wasn't happy."
Third-seeded Tomas Berdych extended his winning streak to eight matches with a 6-3, 6-4 win over Romanian qualifier Marius Copil.
Berdych, who reached the final in Dubai last year, won the Rotterdam title two weeks ago.
Fifth-seeded Jo-Wilfried Tsonga of France secured a 6-2, 6-4 win over Victor Hanescu of Romania.