PARIS, May 28 (Xinhua/Sun) -- Top-ranked Serena Williams was stunned in her defence of the French Open title when she lost to Spain' s Garbine Muguruza 6-2, 6-2 in the second round on Wednesday.

Muguruza, ranked No. 35, used only 64 minutes to score her first victory against a top-eight opponent and hand Williams her most lopsided loss at a major.

Williams looked flat and never found her rhythm, finishing with 29 unforced errors and only eight winners while failing to win a point at net.

The 17-time Grand Slam champion lost five consecutive games after holding to open the match, and she didn' t create any break chance in the first set.

The 32-year-old American quickly fell behind two breaks at 3-0 in the second set and missed an opportunity to begin a comeback when she couldn' t convert at 0-40 while Muguruza served leading 4-1.

"I don' t think anything worked for me," Williams said. "It was one of those days. You can' t be on every day, and, gosh, I hate to be off during a Grand Slam. It happens. It's not the end of the world."

"I think Garbine played really well and she played really smart. I didn't adapt," she added.