PARIS (REUTERS) - Dutchwoman Kiki Bertens showed no ill-effects from her brutal French Open campaign as she eased into the last 16 with a routine 6-2 6-2 win over Katerina Siniakova on Friday (Oct 2).

Fifth seed Bertens saved a match point and was overcome by cramps after her win against Sara Errani on Wednesday, leaving the court in agony seated in a wheelchair.

She had also struggled past Katarina Zavatska in round one and had spent more than five hours on court, so was grateful as she rolled past an error-prone Siniakova in 58 minutes.

Bertens was especially impressive on serve, landing 81% of her first serves in the first set, allowing Siniakova few opportunities to get into the match.

The 28-year-old said the match being switched to under the Court Philippe Chatrier roof because of the rain delays during the day had been a big help.

"The clay was dry, also the balls don't get wet. They're bouncing more. It's easier to serve. Yeah, I think in general in every aspect of my game that's helping me a lot."

Bertens is through to the fourth round for the third time, including a run to the semi-finals in 2016, and after her early problems is looking forward to pushing on.

"It's always special I think when you reach the second week of a Grand Slam. I'm just happy to be here still," she said.

"I'm just hungry for more. I'm just going to see what's going to happen. I'm just going to prepare as good as I can, yeah, then we see again on Sunday."

Bertens faces Martina Trevisan for a quarter-final spot after the Italian caused a shock by beating 24th-ranked Greek Maria Sakkari.

Trevisan's win means two qualifiers have reached the last 16 after Argentine Nadia Podoroska's victory earlier.