The list of competitors continues to thin down as the fourth round of the Men's and Women's Singles at the 2012 U.S. Open are set to take place Monday morning and afternoon. 

Leading the way in Monday's matches will be the Men's No. 1 ranked Roger Federer and No. 4 Andy Murray. For the Women's Singles, Agnieska Radwanska (2) and Serena Williams will be taknig the court as all four players will look to make the quarterfinals of the semis. 

Unranked Tsvetana Pironkova of Bulgaria will lead the way against Ana Invanovic (12) of Serbia. 

Somebody who is surprisingly still alive, Jo-Wilfried Tsonga's nightmare in Week 1, Martin Klizan. He will face Marin Cilic (12) in the closing match at Lous Armstrong Stadium. 

There will be a total of eight matches in Men's and Women's Singles, here they are:

Arthur Ashe Stadium
11 a.m. Tvetana Pironkova vs. Ana Ivanovic
1 p.m.  Andrea Hlavackova vs. Serena Williams
2:30 p.m. Roger Federer vs. Mardy Fish 

8:30 p.m. Andy Murray (3) vs. Milos Raonic

Louis Armstrong Stadium
11 a.m. Nicolas Almagro (11) vs. Tomas Berdych (6)
12:30 p.m. Angelique Kerber (6) vs. Sara Errani (10)
2 p.m. Roberta Vinci (20) vs. Agnieszka Radwanska (2)
3:30 p.m. Marin Cilic (12) vs. Martin Klizan