>> reporter: for serena williams, it was the end of a year-long quest. >> italy's roberta vinci ends serena williams grand slam run. >> i don't want to talk about how disappointing it is for me. >> reporter: just two matches away from the rare calendar grand slam -- winning four majors in the same year. what seemed inevitable to the world number one until a little-known italian, roberta vinci, ranked just 43 in the world. >> i'm happy. i don't know. it's tough to explain my emotion right now. >> i thought she played the best tennis in her career. she played literally out of her mind. >> reporter: williams wasn't the only one shocked to see the unseeded player put an end to her 33-match winning streak. >> this is one of the hugest upsets in all of tennis history. roberta vinci had not beaten serena williams in four tries. >> reporter: for williams, it was an exhausting week. she battled her sister venus on tuesday and after that matched a mitted to being tired. >> i have to wake up early to