Serena Williams won her 19th straight match at the US Open over the last three years; she won the title the last two years in a row. After a rough year at the Grand Slams in 2014 (this is her first Grand Slam semifinal of the year), Serena is hoping to win her 18th career Grand Slam title with another US Open championship, which would be her sixth career US Open title dating back to 1999. She is, as one tennis announcer said (I forget who), the only difference between she and Roger Federer? One is male, one is female. 

Here she is on match point:

After losing the first three games of the match, Serena came back and won the next six in the first set. She won the match 6-3, 6-2 over Flavia Pennetta. She will face Ekaterina Makarova in the semifinals. 

Serena threw in a couple of twirls, including one in the first set and another after she wrapped up the victory: