Six-time US Open champion Serena Williams leads the top half of the draw into the second round on Day Four at Flushing Meadows. Chris Oddo previews the key matchups at wtatennis.com.
 Serena Williams (USA #1) vs. Vania King (USA #87)
Head-to-head: Williams leads, 1-0
Key Stat: Williams can tie Martina Navratilova for the all-time record for Grand Slam match wins with 306 on Thursday.
Serena Williams answered a lot of questions about her injured right shoulder on Tuesday when she mowed down Ekaterina Makarova in straight sets. And that vaunted serve? It's doing just fine. Williams hit 12 aces and won 28 of 31 first-serve points against Makarova, and after the match she shared her joy with reporters. "I was pleased with my serve because I haven't been hitting a lot of serves at all," she said. "In practice, none of them were going in, so I was definitely excited about that." Williams cautioned that she'd have to see how the shoulder feels the day after the match, so it's not an issue that's completely behind her, but all things considered the World No.1 is in great shape and looks on track to make a good run at Grand Slam title No.23. Her opponent on Thursday, fellow American Vania King, has met Williams only once, and only managed one game in that contest.
Pick: Williams in two
 Carla Suárez Navarro (ESP #12) vs. Jelena Jankovic (SRB #40)
Head-to-head: Jankovic leads, 5-3
Key Stat: Jankovic is playing in her 52nd consecutive Grand Slam, which leads all active players.
A pair of well-travelled veterans and fantastic ball strikers will meet for the ninth time in their history and the second time this season on Thursday. No.11-seeded Spaniard Carla Suárez Navarro won the pair's most recent meeting this winter in Serbia, and she has won three of her last four tilts with Jelena Jankovic after the Serb took the first four. Has Suárez Navarro solved the Jankovic riddle, or is there something the 31-year-old 2008 US Open runner-up can do to shake the foundation of the Spaniard? Unless Jankovic raises her level it will be a tough ask. She has struggled to string wins together this season and has not been past the second round at a major since she made the second week atWimbledon in 2015. Meanwhile, Suárez Navarro has been her typical steady self this season. She has gone 18-8 on hardcourts and looks primed to do further damage in New York.
Pick: Suárez Navarro in two
 Simona Halep (ROU #5) vs. Lucie Safarova (CZE #44)
Head-to-head: Halep leads, 3-1
Key Stat: Halep has won three straight against Safarova.
A tricky US Open draw has pitted two top-flight players against one another in the second round in New York. Both Simona Halep and Lucie Safarova came through difficult first-round tests to set a clash of elite talents on Day 4, and even though Halep has won the last three meetings with the Czech, they have not met in over two years. Scorching-hot Halep comes in having won 18 of her last 20 matches and on Tuesday she was ruthless in her 6-0, 6-2 takedown of Belgium's Kirsten Flipkens. Safarova eased past Daria Gavrilova on Tuesday to snap a two-match losing streak. The Czech has encountered a rough patch since Wimbledon, losing four out of five heading into the US Open, but the former world No.5 has the talent to push Halep if she can make first serves and hit through the court from her baseline. That said, Halep's form and fitness should make this a very tough contest for Safarova, even if her level is high.
Pick: Halep in three
 Venus Williams (USA #6) vs. Julia Goerges (GER #64)
Head-to-head: Williams leads, 1-0
Key Stat: Williams is playing in her 72nd Grand Slam main draw, which is most all-time.
She struggled mightily in her three-set win over Kateryna Kozlova in the first round on Tuesday, but Venus Williams found a way to win despite not having her "A" game. Like she always does, the No.6 seed took the positives from the effort and is now ready to turn the page. "The first round is never easy," she said after increasing her record to a perfect 18-0 in opening-round matches at the US Open. "You're trying to find a rhythm, get used to the court… But it was great to be challenged and to be pushed because I had to get in those situations that you know you're going to face in the tournament early on. So that felt good to come through." Williams moves on to face a talented German who likes to go on the attack early and often in Julia Goerges. In their lone previous meeting, Williams secured a 6-4, 6-3 win. A victory on Thursday would bring Williams' all-time US Open win total to 70, which is second among active players and fifth-most all-time
Pick: Williams in three
By the Numbers:
154 - Number of victories, combined, that Serena and Venus Williams have earned at the US Open.
416- Karolina Pliskova's 2016 ace count in 46 matches. She'll meet qualifier Montserrat Gonzalez in the second round today.
305 - Serena Williams current total of Grand Slam victories is just one shy of the all-time record of 306 which is held by Martina Navratilova. Her US Open win total of 85 is third behind Navratilova (89) andChris Evert (101).
– but the sailors praise the new boats