By Martyn Herman
PARIS (Reuters) - Top seed Novak Djokovic's untroubled progress continued at the French Open as he chalked up a fourth successive straight-sets victory on Monday, this time outclassing Jan-Lennard Struff to reach the quarter-finals.
His 6-3 6-2 6-2 defeat of the 45th-ranked German means Djokovic is the first man to reach 10 successive quarter-finals at Roland Garros -- a feat even Rafael Nadal has not achieved.
Struff was bidding to reach his first Grand Slam quarter-final and provided some early resistance in drizzly conditions on Court Philippe Chatrier.
Djokovic had an early chance to break in the second game but Struff won a fierce baseline rally to avert the danger.
It felt like only a matter of time before Djokovic moved up a gear though, and in the seventh game he brought up two more break points with a stunning backhand passing shot.
He duly converted with a smash after softening up Struff with a series of punishing groundstrokes into the corners.
After holding serve to take the opening set, Djokovic rolled through the next two in cruise control, making only 11 unforced errors in the one hour 33 minute workout.
He will face either Italian Fabio Fognini or German's Alexander Zverev in the quarter-final.
Djokovic is bidding to become only the second man to hold all four Grand Slams simultaneously twice, having first achieved the feat three years ago when he won his only French Open title.
(Reporting by Martyn Herman; editing by Tony Lawrence)