NEW YORK, NY, USA - Serena Williams has been cruising so far this US Open fortnight, the only player remaining not to surrender a set. In fact, Williams has dropped just 16 games. Nevertheless, she should beware as she prepares to take on Sara Errani in Friday's semifinals. In quite a few of her previous Grand Slams in which she was especially dominant prior to the final four, she ended up getting beaten.

"I feel like I'm going to get more focused and serious and start playing Serena tennis in the next couple of rounds, if I get to play two rounds. That's my goal," Williams said. "I didn't think I came into this tournament playing my best, but I definitely played better in the last two matches. I hope I have two matches left."

Here are the majors in which Williams gave up the least amount of games entering the semifinals and how far she ended up going: