U.S. Open Day 8 matches to watch: Serena Williams, Roger Federer in day time

Murray has a 1-2 record against Raonic. (Getty Images)

Week 2 of the U.S. Open is upon is. Now things really get fun.

Half of the women's draw has already played the Round of 16 and on Labor Day the rest of the women's quarterfinals will be set. There were a couple of upsets on Sunday so we'll have to see if the bottom half of the draw finds the same fortune (or misfortune for the higher seeds).

The men meanwhile begin their Sweet 16 and all but one of the spots are held by players who came in seeded in the top 23. Written another way that means we've got some big matchups coming our way.

Reminder: The tournament is on CBS and the CBS Sports Network during this three-day weekend. You will also be able to watch the matches live right here on CBSSports.com from 11 a.m. to 6 p.m. ET. Another reminder: Start times are not precise.

11 a.m.: Ladies first in the biggest stadium in tennis, Arthur Ashe Stadium. Ana Ivanovic, who faced her toughest match thus far on Saturday but got through young American Sloane Stephens in three sets, is staring down Tsvetana Pironkova of Bulgaria, an unseeded player who has yet to face a seeded opponent up to this point.

For Ivanovic it's the third straight year playing in the fourth round of the U.S. Open but she hasn't been to the quarterfinals in a long time ... in any Slam event. You have to go all the way back to the one and only Slam title of her career at the French Open in 2008 to find a time Ivanovic hit the quarters in a major. She has never been to the quarters at the U.S. Open.

At the same time the day in Louis Armstrong Stadium will begin with the men as Tomas Berdych and Nicolas Almagro, one that won't have the most attention but could produce some solid tennis. Almagro's game on the hard court has grown tremendously to the point that he can't just be called a clay-court specialist. He's more than a tough out for the 6th-seeded Berdych. This match has "long" written all over it.

The two met on the hard courts of Indian Wells earlier this summer and Almagro took it somewhat easily, winning 6-4, 6-0. It will be their fourth matchup of the year (Berdych beat Almagro in the Aussie Open).

1 p.m.: For Serena Williams it will be an earlier than usual start at the U.S. Open but she'll take to Ashe for the second match of the day with another quarterfinal spot up for grabs. Thus far Serena hasn't been challenged very much at all but the same can't be said of Hlavackova. The Czech who checks in at 82nd in the world rankings has gone through two seeded players to get this far, including her upset of Maria Kirilenko in the third round.

It's imperative for Hlavackova to get off to a strong start because Serena has gotten stronger as each match has progressed.

2 p.m.: The best match of the day that nobody is talking about? It will most likely be the second match of the day on Armstrong, No. 6 Angelique Kerber vs. No. 10 Sara Errani. Kerber's success is documented, she took out Venus Williams in a great second-round match and is enjoying by far the best season of her career. She was a semifinalist her a year ago.

It's Errani that is the most intriguing in this matchup. Since losing the second set of her first match in a tie-break, Errani has been invincible it seems. She has dropped only four games in five sets since then, never more than one game in a set. That's cruise control. They have only played twice with Errani winning at Roland Garros but Kerber taking their only matchup on the hard courts.

3 p.m.: What was supposed to be a match between Roger Federer and Mardy Fish in Arthur Ashe Stadium took a different direction when Fish had to withdraw.

Instead, the late match on Armstrong between No. 12 Marin Cilic and Martin Klizan, the most surprising (and only unseeded) player in the final 16 on the men's side. The Slovakian pulled the upset of the men's tournament so far when he seemed to almost bully No. 5 Jo-Wilfried Tsonga and then followed that up by taking out another Frenchman, Jeremy Chardy.

4 p.m.: The ladies continue sorting out the quarterfinal spots on Armstrong where No. 2 Agnieszka Radwanska faces No. 20 Roberta Vinci. Radwanska is the second seed but you haven't heard much about her one bit, and there's a reason for that. For one she might be ranked second in the world but most would agree that she's not the second-best player with Victoria Azarenka, Maria Sharapova and Serena Williams around.

Moreover, Radwanska has never reached the quarters at the U.S. Open. So she doesn't have a track record of success at the Open. But she is coming off a win over Jelena Jankovic who isn't quite the player she used to be but that can still be a confidence boost.

An interesting wrinkle in the equation is that Vinci has the chance to beat a member of the Radwanska family for the second time in this tournament. She defeated Aga's younger sister Urszula in the first round, 6-1, 6-1.

7 p.m: For the second time of the day, Serena Williams will take to Ashe Stadium, this time with her sister Venus in their doubles match with the fourth-seeded team of Maria Kirilenko and Nadia Petrova of Russia. In their previous two matches the Williams sisters have followed the same script: Play a tight first set then bagel your opponents in the second. The doubles draw opened up with the defending champs losing over the weekend so this match can go a long way in deciding the doubles championship.

9 p.m.: Hopefully the match begins sometime around then and it doesn't go until 2 in the morning like the action did on Sunday night/Monday morning because this match has some real intrigue. The No. 3 seed Andy Murray gets his toughest test yet in this tournament with No. 15 and hard-serving Milos Raonic of Canada.

Murray had his hands full last round, needing tie-breakers for all three of his set wins against Feliciano Lopez. With Raonic on the other side of the net, Murray could be looking at more tie-breakers, but that isn't exactly where you want to be against a guy with as strong a serve as the young Canadian has.

Raonic has yet to reach the quarterfinals of a Slam in his career so if he's going to get that first breakthrough he'll really have to earn it vs. Murray.