Four-time champion Novak Djokovic reached the second round of the Dubai Duty Free Tennis Championships with a 6-3 6-3 win over Uzbekistan Denis Istomin.

Djokovic was playing for the first time since his quarter-final exit to Stanislas Warwinka at the Australian Open.

“It wasn’t as easy as the scoreline indicates,” the top seed and defending champion told www.atptour.com.

“I needed to work for my games. My serve worked really well in the second set, and that helped me to get some free points.

“But having not played for more than four, five weeks, an official match, obviously it takes its toll on the court.”

Second seed Juan Martin del Potro was an early casualty as he retired after losing the a first-set tie-break to Indian wild card entrant Somdev Devvarman 7/3.

Del Potro, fifth on the ATP rankings, went immediately to the tournament doctor after the loss.

“It’s hurting all the time, sometimes less and sometimes more. My (US) doctor is trying to keep me motivated to keep playing, but I know my limit on court – today was enough,” he said.

It was otherwise smooth progress for the seeds as Tomas Berdych (three), Jo-Wilfried Tsonga (five) and Mikhail Youzhny (six) all won.

Berdych beat qualifier Marius Copil 6-3 6-4 while Tsonga set up a second-round meeting with Nikolay Davydenko after outclassing another Romanian, Victor Hanescu, 6-2 6-4.

Youzhny beat Michal Przysiezny 6-3 6-4 and will play British wild card James Ward in the next round.

Tunisia’s Malek Jaziri made it three wild cards to go through after he recovered from a ‘bagel’ in the first set to beat Igor Sijsling 0-6 6-4 7-6 (7/4).

Jaziri’s reward in a second-round meeting with Devvarman.

Elsewhere, veteran Radek Stepanek booked a meeting with Roger Federer following a 5-7 6-3 6-1 win over Michael Russell.