Serena Williams can dominate women's tennis for another four years as her former coach Rick Macci backed her to complete the Grand Slam.
Williams, 33, heads to Flushing Meadows looking to claim her fourth grand slam of the year and 22nd overall.
The veteran American would become the first player since Steffi Graf (1988) to win the Grand Slam.
And she is not done yet, according to Macci – who coached Williams from the age of nine to 15.
"I think that Serena can stay at the top of the women's game for another three, four years. This is all predicated on her health," he told Omnisport.
"If she is injury free, I mean one ankle, knee, shoulder you know that could derail this whole thing. But she has been relatively injury free lately and she is in control. She knows that.
"And she knows that when she is in a tournament she can win it anytime. I could see her if she wanted to play until she is 40. I really could. I think it's in her blood.
"She loves to compete; she loves to knock people out. She goes back when I told you she was nine years old. She thrives on competition and you can feel that coming through your TV set. She loves to compete. So that alone will keep her going. Not discounting she can win any tournament.
"And she is winning millions of dollars, that is a good reason to keep playing. But I see her playing for a long, long time still."
Macci also believes Williams will overtake Margaret Court for the most grand slam titles ever won.
With 21, Williams is still behind Court (24) – but Macci said he knew the record was achievable from when Serena was a teenager.
"I think Serena will complete the Grand Slam," he said.
"When she hit 17 or 18 I told one of the journalists from the NYT [New York Times] or WSJ [Wall Street Journal] you know I think she will get 26 or 27. I think this is all in her hands.
"A lot of people who were one, two and three in the world or have won grand slams in the past few years, they've all exited stage left."