Serena Williams playing her last tennis tournament ''US open''
Serena Williams will open doubles play with her sister Venus
Williams defeated Danka Kovinic 6-3, 6-3
Serena Williams is now 40 years old
Serena Williams announced her retirement from tennis early this month
Serena Williams said, it was a difficult decision for her to move on
Fans gave a Tribute To Serena Williams After Match