Second-round play began on the many courts at the Billie Jean King Tennis Center on Wednesday as former champions headlined the action.

Serena Overcomes a Slow Start to Advance

World No. 1 Serena Williams continued to work towards a calendar year Grand Slam against Kiki Bertens on Wednesday. After an opening-set struggle, Williams advanced 7-6, 6-3.

Perhaps the top seed felt the pressure of her potential historical feat against the Dutchwoman. Struggling from the beginning of the first set, Williams appeared out-of-sorts, particularly where her serve was concerned. The American, openly frustrated, was forced to come from behind after Bertens gained an early break. But in what has been witnessed at other majors this season, she would fight through her difficulties and despite eight double faults in the first set, would force a tiebreak.

The veteran would dig a 0-4 hole at that stage before Bertens would play a stretch of nervous points, allowing Williams back into the tiebreak. And after a fortunate let cord on set point, Williams found a way to win another set in which she failed to play near her capabilities.

In the second set, Serena appeared to play much less stressful tennis, and although she did not play her best, it was enough to advance. However, to avoid an upset in New York, she will need to serve at a much higher level. On Wednesday, the American placed only 59 percent of her first serves in play and tossed in 10 double faults.

Williams was clearly not happy with her level of play. “It definitely wasn’t my happiest of moments,” she said. “I don’t think you should be happy with just winning. At least I’m not. Maybe other people can.”       She will face American Bethanie Mattek-Sands in the third round on Friday.

Djokovic Impressive in Victory

Top seed Novak Djokovic closed down the night in Ashe Stadium against Andreas Haider-Maurer. And in a crisp, solid performance, he advanced in straight sets 6-4, 6-1, 6-2.

In a competitive first set where each player’s serve was difficult to crack, it was the Serb who finally broke through as Haider-Maurer attempted to stay in it. With the Austrian serving at 4-5, Djokovic broke at love despite a solid set by the big server.

In the second set, Djokovic measured Haider-Maurer’s serve and successfully held his as the match tilted heavily in his favor. As the contest progressed, Haider-Maurer’s first-serve percentage decreased. The nne-time major champion took full advantage of his opportunities against his opponent’s less productive second serve and opened up the match. It was an impressive performance by a competitor who is seeking his third major championship of the season. Concerns about Djokovic’s level of play following his Wimbledon title are fading deep into memory.

With the victory, Djokovic will face Andreas Seppi in the third round on Friday.

Nadal Advances in Straight Sets

After struggling for a good portion of 2015, the former world No. 1 appears to be finding his game of late. In the first round, Nadal showed glimpses of the type of play that led him to a multitude of championships. And while he is still a distance away from the player who has won 14 major championships, he may be able to build upon his early results in Flushing Meadows. Still searching for confidence at times, Nadal dispatched Diego Schwartzman 7-6, 6-3, 7-5.

In the first set, Nadal came out sharp and jumped out to an early lead. But some tentative play midway through the set allowed Schwartzman back into it as the unforced errors piled up for the Spaniard. The set moved into a tiebreak, where Nadal uncharacteristically struggled with his forehand, giving away a few tense points. However, despite his difficulties, Nadal would take the tiebreak at 7-5 and would win a set that had looked routine early.

At times in the second set, Nadal did not appear to attack the ball with the same intensity as in the early stages. However, he fought through lapses to gain control and after cleaning up some unforced errors, he would close out the set. In the third set, he would drop an early break to the Argentine but battled back for service breaks of his own in two out of Schwartzman’s last three service games. Nadal would advance despite 40 unforced errors in the match. He would offset that somewhat with 38 winners.

Nadal was happy with his serve but felt his level could have been higher. “Today, I felt that I was practicing great before the match, and yesterday, too. I felt that during the match I didn't arrive to that high level that I was practicing before,” he said. “But it's true that he played really well. Even if he had a break up in the second and in the third, I had a lot of 0-30s, 15-30s, a lot of opportunities during the whole match to have I think a more comfortable victory.”

Venus Survives a Strong Effort from Falconi

One player who could stand in the way of Serena Williams is her sister Venus. The two could meet in the quarterfinals if both advance. Venus found her hands full with the feisty Irina Falconi. but she would earn the victory, 6-3, 6-7, 6-2.

Williams looked as if she would overpower Falconi in the first set, but the scrappy American fought on every point and tightened the set. Venus found success approaching the net and with too many errors off the Falconi racket, she closed out the set comfortably.

However, the second set was not as easy for the older Williams sister. Falconi kept her under pressure with aggressive groundstrokes, moving Williams around the court. Her spike in aggression paid off as Williams twice failed to serve out the match. With her confidence swelling, the 25-year-old forced a tiebreak.

Led by her cross-court backhand and a never say die mentality, Falconi dominated the tiebreak, forcing a decisive third set.

In the third set, Williams built an early lead once more after a service break. She sought to attack the net, where she found success earlier. And this time she would close the match out with another break of service.

The 35-year-old indicated that she received a wake-up call after dropping the tiebreak. “She played a great tiebreaker,” Williams said. “In the third set, I felt like I had a lot more clarity.”  She will meet the red-hot Belinda Bencic, who recently defeated Serena, next in the third round.