After another early round shaky start, followed by a drama-filled recovery, Serena Williams moved another rung higher on tennis’ ladder of greatness at the U.S. Open. Trailing 5-3 in the first set, Williams rallied to beat Kiki Berkins, of the Netherlands 7-6 (7-5), 6-3 in the second round. The victory moved Williams a step closer to her fourth consecutive U.S. Open title, but more importantly, she remained on course to become only the fourth woman in tennis history to capture the Grand Slam — Australian Open French Open, Wimbledon and the U.S. Open in a calendar year. No player has won the Grand Slam since Steffi Graf in 1988. If Williams wins her next five matches, she’ll have 22 major titles, same as Graf.

Williams admitted that she was “a bit tight” when Berkins led 5-3 in the first set, but said she never doubted that she would find her game and win the match. “I just focused,…thought to take it one point at a time,” she said. “Being down a lot, I know I can come back, make a run for it. When I get down, I tend to relax and start playing better. I’ve always made legendary comebacks. That’s been my MO (method of operation) my whole career.”

Said Madison Keys: “I think her drive and fight is unmatched by anyone. When she’s down .. you can never really think, Oh, Serena’s going to lose this match. You always have this feeling that she can come back from anything. She’s amazing to watch.” No. 19 Keys, who defeated Tereza Smitkova, Czech Republic, 6-1, 6-2, could face top seed Williams in the fourth round.

With the sports world – and indeed much of the non-sports – watching her every move, Williams has struggled in the last few months to suppress her anxiety. Against Bertens last night, she punctuated more than a few of her groundstroke or return of serve winners with high-pitched screams of satisfaction.

“I don’t think you can underestimate the pressure she’s under,” said Patrick McEnroe, an ESPN analyst and former pro. “There’s also no doubt that she can certainly handle it. You’ve got to give her a lot of credit. “

Patrick’s Hall of Fame brother, John, who won seven major titles (4 U.S. Opens, 3 Wimbledons) says Serena is “the greatest player that’s every played,” even if she doesn’t win the U.S. Open. “Even when she’s not playing her best, she figures out a way to win,” John McEnroe said.

Williams next plays fellow U.S. pro Bethanie Mattek-Sands, who defeated Coco Vandeweghe.

“She’s an aggressive player,” Williams said. “I know I’m going to have to start out strong if I want to stay in the tournament. If I don’t play well, I’m not going to be happy.”