HARRISON, N.Y. — The Henderson family experienced failure last week. Before arriving at the Manulife L.P.G.A. Classic a few hours from their home in Ontario, Brooke Henderson and her father, Dave, had talked about the goal they wanted to hit during the week. Dad is the caddie and, knowing his daughter’s game as he does, said that three under par would be ideal. Brooke agreed.
Through the first 36 holes of the event, Brooke Henderson shot three under. But last week’s cut was the lowest in tour history, and she missed it by a stroke.
“It totally caught us off guard,” Dave Henderson said. “It was one of those things where we were successful — but were we? We took a look at our goals and decided to reassess what was successful.”
He was recounting this story Friday while standing on the back-patio area behind Westchester Country Club’s pro shop in the early afternoon. Behind him was a small, hand-operated leaderboard for the Women’s P.G.A. Championship, where the volunteers had just finished putting “Henderson” up in the second position with a two-day score of six under. Brooke is two strokes back in just her third career major championship.
She is 17 years old.
“I don’t really think age has much to do with it,” she said. “I think it’s more about the experience. Even Lydia Ko has said that before — that it’s experience, not so much the age. I think we don’t have a lot of fear. That’s one of my mottos I try to stick with, is ‘no fear.’ And just try to be aggressive and play my own game.”
Henderson is not even a full-time member of the L.P.G.A. Tour, which requires members to be at least 18. She will not celebrate her birthday until Oct. 9. Her family petitioned for a waiver that would have permitted her to try to qualify through the L.P.G.A.’s Q-School, but the Hendersons were rebuffed.
The only way she can qualify for full-time status and bypass Q-School is to finish the season in the top 40 on the money list. So far she has earned $184,745, playing in seven events. Last season on tour, the player who finished 40th earned $447,658.
For now, Henderson must rely on sponsor exemptions — she has one for this week — or getting into the field through Monday qualifiers. But she can use only six exemptions in a single season, and the Women’s P.G.A. Championship is her fifth. (Her last exemption will be the Canadian Pacific Women’s Open at the end of August.)
She has qualified for the United States Women’s Open next month and is working toward an exemption for the Women’s British Open, but that will not count toward her tour number.
That means a victory this weekend, when the winner will earn $525,000, would all but cement her status on tour for next season.
“We’re being told that she has to win to get on the L.P.G.A.,” her father said. “So we’re going to try and do that. But it’s a major. They’re going to make it tough.”
The field will not make Henderson’s task any easier. During a second round in which the friendly scoring conditions from the first day had disappeared, Sei Young Kim shot five under in the afternoon to hold the lead at eight under par.
The 40-year-old Karrie Webb — a seven-time major winner — and the event’s two-time defending champion, Inbee Park, both sit at seven under. Stacy Lewis, ranked No. 3, is tied with Jenny Shin at five under.
“I just love the variety of people we have on the leaderboard,” Lewis said. “You’ve got Karrie, who is 40, and then you’ve got a bunch of 17-year-olds chasing her, and I’m somewhere in the middle. It’s pretty cool to see just how the game of golf is ageless, really.”
It just will not allow a player in through the front door unless she has reached a magic number.
For Henderson, a win at Westchester and the tournament’s first-place prize money would go a long way toward making sure she is a fixture on the L.P.G.A. Tour. So Henderson, just as she did after missing the cut last week, is readjusting her goal.
“It’s really exciting seeing my name up there with Stacy Lewis and Karrie Webb and all the big names,” she said. “It’s awesome. I think I just have to stay patient, stay consistent and keep working on my game, and I think good things will happen.”
An earlier version of this article misstated the number of strokes separating Brooke Henderson from the leader, Sei Young Kim, after the second round of the Women’s P.G.A. Championship. It was two, not one.