Novak Djokovic guaranteed his record-breaking time at the top of tennis' world rankings would continue after his second-round win at the Madrid Open.

The Serbian star beat Gaël Monfils 6-3 6-2 on Tuesday, guaranteeing he would remain as world No. 1 for a record-extending 369th week.

The win also extended his perfect record over the Frenchman to 18 from as many matches, meaning he becomes the first man in the Open era to hold an 18-0 ATP head-to-head against an opponent.

Djokovic will now face three-time grand slam winner Andy Murray in the last 16 after the British player stunned Denis Shapovalov 6-1 3-6 6-2.

“I don't have any explanation for that, I just try to approach it like any other match,” Djokovic said of the record against Monfils.

“I guess his game is suitable to my game in terms of playing style. But we've had some very close matchups. The last time we played in Dubai he had match points, so that could have easily broken the record.

“I don't think about that too much. For me mentally, this is a very important win.”

Although Monfils showed why he's one of the most entertaining players to watch, once 20-time grand slam champion Djokovic saved three break points early on, Monfils never troubled Djokovic at the Manolo Santana Stadium.

Monfils won the winner count, 18 to 11, but Djokovic showed his experience and know-how.

Playing in just his fourth tournament since returning from a tumultuous time away from tennis, Djokovic is still working his way to his best form.

“I played one of the most athletic and quickest players that we have in the game,” Djokovic said. “I know his game very well. I know I have to always be ready that another ball will always come back from his part of the court that you have to constantly try to have a controlled aggression ... and dictate the point.

“I was moving well, dictating with the forehand side, moving him around the court and finding my serve (and) also the last few service games, (finding my) return.” (CNN)