PARIS, May 28 (Reuters) - Novak Djokovic's hopes of completing a career grand slam by winning the French Open suffered a scare when he needed a medical timeout during a 6-1 6-4 6-4 win over Luxembourg's Gilles Muller at Roland Garros on Thursday.

The Serb top seed slipped on the clay during the second set of the second round match and stretched his right groin muscle, calling for the physio at the change of ends after the ninth game.

Apart from that it was a straightforward victory as he dropped serve only once.

After converting match point with a service winner he went and shook hands with Paris St Germain striker Zlatan Ibrahimovic who was watching in the crowd.

Djokovic will next face Australian hot prospect Thanasi Kokkinakis with a potential quarter-final clash against nine-times Roland Garros champion Rafa Nadal looming.