Updated

By Martyn Herman

PARIS (Reuters) - Sickly Serena Williams suffered a dizzy second set during her third-round match at the French Open on Saturday, but recovered her senses in time to beat Russia's Anastasia Pavlyuchenkova 6-1 1-6 6-2.

The American world number one needed a check-up from a doctor after dropping five consecutive games to her 18-year-old opponent in the second set and admitted afterwards that she was not feeling well during a scrappy match.

"I just got a little dizzy. I don't know. I got really fatigued. I felt really dizzy out there. I was just trying just to stay in there," the 28-year-old told reporters. "Just fighting a cold and fighting sickness.

"(The doctor) said that there's a bug that's going out. Players start feeling tired and the next day they get sick. I'm gonna load up. I've been loading up on vitamins. I should be okay. I hope."

Williams, watched by sister Venus who was wrapped up against the mid-morning chill on a grey, breezy day in Paris, lost her opening service game when a drop shot caught her napping but she looked fine as she rattled off the next six games.

A nervy Pavlyuchenkova forgot her inhibitions in the second set and stretched her opponent with some powerful ball-striking although she was aided by a raft of errors off the American's racket as she raced into a 5-0 lead.

Williams avoided a shut-out when she held her serve but was still looking groggy in the early stages of the deciding set when Pavlyuchenkova had two break points at 1-1.

She saved both, one with an unreturnable forehand and the second with an ace, and proceeded to take control, completing a one hour 48 minute victory when she drilled a return to the feet of her dispirited opponent.

"Definitely toward the end of the third I started feeling better and moving better, and then I was able to play some longer points, so that's a good sign," Williams said.

She was spared any further running on Saturday when her and sister Venus were given a walkover in the doubles second round by Daniela Hantuchova and Caroline Wozniacki.

She will have until Monday to recover for her next singles assignment when she takes on Israel's Shahar Peer.

(Editing by Miles Evans)