NEW YORK - Here are five things to watch on Day 4 at the 2010 U.S. Open.

1) Stars under the lights
While Novak Djokovic started to make his presence felt in the tennis world in 2006, his breakthrough year was in 2007, when he made it to the semifinals at the French Open and Wimbledon and the final at the U.S. Open. It was also that year that he became a crowd favorite, delighting the fans at Arthur Ashe Stadium one night with his impressions of Rafael Nadal and Maria Sharapova.

If he shows off his imitiations again on Day 4, fans at Arthur Ashe will have an easy time determining how accurate his aping is. No. 14 Sharapova will be No. 3 Djokovic's lead-in match in the Sept. 2, 2010 night session.

After surviving a first-round scare, Sharapova will take on Iveta Benesova of the Czech Republic in the second round. The Russian holds a 2-0 career edge against Benesova, with her most recent victory coming in straight sets in the 2009 Tokyo tournament.

Djokovic also was pushed to the limit in his first-round match but ultimately pulled out a five-set victory on the hot afternoon of Day 2. His second-round opponent is Germany's Philipp Petzchner, who never has previously made it past the second round at the U.S. Open and is ranked No. 52 in the world. But Petzchner's first-round win took just under an hour and a half to complete, and he may be the fresher of the two. This will be the players' first-ever meeting.

2) Fish on the hook
Highlighted as one of the players to watch this year at the U.S. Open due to his impressive summer success, No. 19 Mardy Fish nearly flamed out in the first round. But his five-set win may have given him the scare he needs to refocus and come out strong on Day 4.

No. 88 Pablo Cuevas will try to accomplish what Fish's first-round opponent couldn't and send the American packing. The two right-handers never previously have played each other.

3) Blake looks to continue his run
Showing a spark in front of a supportive Day 2 crowd, James Blake eased his way into the next round with a straight-set victory. It was a big win for Blake, who had looked vulnerable to an early exit after a lackluster summer season and lack of recent success. But his strategy of switching up his play by coming to net on select points paid off, and he delivered big shots in key moments to move on.

Blake's second-round opponent won't be an easy player to defeat, however. After playing his way through the qualifying field to earn a spot in this year's main draw, Canada's Peter Polansky shocked No. 30 Juan Monaco in straight sets on Day 2. He'll be riding high coming into his Louis Armstrong match and could end Blake's 2010 U.S. Open run.

Slideshow   Flushing fashion Images of some of the outfits worn by players at the 2010 U.S. Open.

4) Dent wants revenge against Soderling
After being demolished by Robin Soderling by a 6-0, 6-1, 6-1 score in the second round of this year's French Open, Taylor Dent will be looking for revenge against the No. 5 seed on a surface where Dent feels more comfortable. They are the third match on the Grandstand on Day 4. With his French Open win, Soderling improved his career record to 2-1 against Dent, with the American capturing his lone victory in four sets at the U.S. Open in 2003.

5) Another hot day
U.S. Open action on Day 3, where court temperatures on Arthur Ashe skyrocketed over 100 degrees, featured a number of upsets, seeded players struggling and players being negatively impacted by the heat. They won't get any relief in Thursday action, where similar conditions are predicted. If temperatures climb high enough like they did Wednesday, extreme heat rules will be put into effect, although that provides only a little bit of relief for the players toiling on the court. Look out for those competitors who are the most fit or who have experience with the heat to excel on Day 4.

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