Here are my five to watch on Day 4 as the majority of second round gets underway.
Venus Williams (USA) vs  Angelique Kerber (GER) Arthur Ashe Stadium (H2H Angelique Kerber 2-1)
This is definitely the standout match of the day as last year’s semi finalist takes on the two time champion to close the night session. With Day 3’s night session seeing another two one sided matches in which the loser took seven games over the five sets played, this match should appease those hoping for more competitive matches on the showpiece court. With what looks like an easy passage to at least the quarter finals, perhaps the semi finals, there is a lot at stake. The pair have played each other twice this year with Kerber coming out on top in straight sets over two different surfaces, suggesting that she now has the upper hand over her more experienced opponent.
 Marcel Granollers (ESP) vs [WC] James Blake (USA) Louis Armstrong Stadium (H2H Marcel Granollers 1-0)
James Blake’s reward for defeating Lukas Lacko in the first round is another appearance on Louis Armstrong Stadium, but he can expect a tougher time in this round against his Spanish opponent. Granollers has been somewhat underrated in the past and most recently quietly moved in to the top 20 for the first time but has now dropped back down to 24. Having defeated one American in Denis Kudla in the first round, he will be hoping to double his tally. Blake and Granollers have met just once, in a clay court encounter in Houston 2008 where Granollers was a shock victor. James Blake is still a delight to watch at times and still showcases his venomous forehand from time to time but cannot afford to have too many blips on serve like he did in the first round.
Carla Suarez Navarro (ESP) vs  Agnieszka Radwanska (POL) Grandstand (H2H Agnieszka Radwanska 2-0)
Since her Wimbledon defeat, the second seed has seen quite a drop in her usually incredibly consistent form. While losing to Na Li in this form isn’t embarrassing, the ease with which the Chinese dealt with her was very surprising. Radwanska took just five games in over their two encounters and struggled to hold serve throughout. New Haven saw her retire against Olga Govortsova at 0-6 1-2 down and if still suffering, Carla Suarez Navarro could possibly give her a scare. While primarily a clay player, recent wins over Sabine Lisicki on hard court and Samantha Stosur (despite her grass troubles) should still give the Spaniard confidence.
Paul Henri Mathieu (FRA) vs  Milos Raonic Court 17
After both players won in five set epics last time out, they will be hoping for a much quicker match this time round. Mathieu came from two sets down, saving match points to defeat Igor Andreev while Raonic came from 2-1 and a break down to eventually down Santiago Giraldo. When someone serves 30 aces, it seems odd to say that someone is having serving trouble but this was definitely the case with Raonic who served a massive 15 double faults and served just 54%. There is no denying that the serve is near unbreakable when working and it should be a much easier time for the Canadian if he can avoid the errors he made in the last round. Mathieu’s mental strength has often been called into question but his performances in five sets at recent slam events suggest that he is improving since his return from a bad knee injury.
Yaroslava Shvedova (KAZ) vs  Roberta Vinci (ITA) Court 11
Vinci will be high on confidence after taking the title in Dallas last week with victory over Jelena Jankovic. Her slicing ability has the potential to frustrate many an opponent and did so to full effect last week. She did not drop one set throughout the tournament and rescued difficult positions in the final to win in straights. Shvedova has finally burst back onto the scene after injury with two straight appearances in the second week of a slam, taking top 10 scalps in both tournaments and famously winning her golden set. She found it quite easy in the first round against her good friend Vania King but it will be much tougher here. Shvedova is well capable of a shock here if she has got over the illness that has plagued her in the past two weeks.