David Cooke is having a summer to remember on the golf course, thanks in large measure to someone whose words helped to inspire that success.

On July 22, Cooke shot a final-round 63 to capture the Illinois Open by five strokes, the largest margin of victory in the event in nearly 40 years. And on Wednesday, he posted a 3-and-2 victory over Hank Lebioda to move into the Round of 32 in the U.S. Amateur, the most competitive championship in amateur golf.

“I think he’s been with me ever since it happened,” said Cooke, 22, of his late brother, Chad, whom he lost eight months ago when Chad, then 20, collapsed and died as the two played pickup basketball over the winter holiday break. “He was a big supporter of mine and he was always trying to encourage me to do my best and to believe in myself, to not be scared of anything.”

The brothers grew up in Bolingbrook, Ill., and their family recently moved to Lisle, Ill., about 45 minutes from Olympia Fields Country Club. David was home from North Carolina State, where he plays golf, and Chad was home from the College of Charleston, where he had been a walk-on member of the basketball team. They begged out of wrapping presents on Dec. 23 so they could play some full-court, three-on-three basketball. After 90 minutes of play, Chad collapsed on the court and died, apparently of cardiac arrhythmia.

David struggled with anger and anguish in the months after the loss of his brother. More recently, he recalled Chad’s words shortly before he died, as the brothers mulled internship applications for this summer, David’s last before graduation.

“He was always telling me, ‘You’ve got to try golf – you’ve got to put everything into it while you can,’” said Cooke. “He was always a big dreamer, and I definitely think that he’s given me the strength and the courage to believe that I can do it.”

Cooke nearly opted not to go back to school in January because, as he later explained to the Raleigh News & Observer, “I didn’t want to go by myself, be by myself.”

His support system at college includes his coach, Richard Sykes, who told the newspaper, “It was like he wanted to spare us his grief, to keep us from hurting for him.” Cooke did not want to travel to the team’s first event of the spring, in Puerto Rico, before relenting and playing poorly. Later he captured the Wolfpack Spring Open, his second tournament win of the school year.

“I knew he would want me to keep playing,” said Cooke of his brother. “He was a big advocate of going at it with all you’ve got and not being scared to be successful.”

Cooke’s recent success is unprecedented.

“This summer has gone well for me just because I always remind myself I can do it,” said Cooke, who led N.C. State with a 72.2 stroke average in 2014-15. “I’m just as good as anybody – it’s just a matter of believing that I am.”

Cooke’s older brother, Jay, 34, caddied for him in the Illinois Open, a role that Chad had filled in past events. His parents and grandparents, in addition to other family members and friends, are part of his gallery this week.

“I got off to a good start – I made birdie on the first two holes [to go 2 up],” said Cooke of his victory over Lebioda, which earned him a place in the Round of 32 opposite No. 2 seed David Oraee, of Greeley, Colo., at 8:20 a.m. on Thursday. “I just tried to hit good shots and put the pressure on him. If I keep hitting greens and giving myself looks, I’m going to ride it out as long as I can.”

Cooke readily admits that his attitude has changed since the loss of his brother, who helped out in the Charleston community through Charleston Hope and Adopt a Classroom, a program that was founded by his girlfriend. In typical fashion, Chad pushed her to expand the scope of the efforts to provide holiday presents for local youngsters in need.

“I definitely put forth the effort to be as good as I can be,” said David. “But I’m trying not to get too caught up in it, not getting super-upset about bad shots, not really worrying about if I slip up in certain instances. Getting upset is just going to get in the way of me doing the best that I can.”

Cooke, who calls himself a late bloomer, has played in one previous USGA championship, last year’s U.S. Amateur Public Links in Newton, Kan., where he failed to reach match play.

“It’s a good feeling knowing that all the best guys in the country and the world are here, that if I do well, it’s the biggest stage in amateur golf,” he said. “It also exposes your weaknesses – you think you’ve played well and you see that the [medalist] shot 7 under. That’s as good as you’ll ever see.”

He relished the opportunity to play on Thursday at Olympia Fields, where a comfort level has been developed.

“Growing up nearby, I’ve always loved playing here,” said Cooke. “It’s probably my favorite club in the Chicago area. After I qualified for the Amateur, I came out here a few times beforehand. It’s a huge benefit to see how differently some holes play with different winds. It’s a factor, even when you can’t feel it.”

Like the wind that can’t be felt on the ground, emotions that can’t be seen or verbalized – like the unwavering belief of a younger brother – will endure at Olympia Fields and beyond.

Ron Driscoll is the manager of editorial services for the USGA. Email him at rdriscoll@usga.org.