Eight years later, Spieth is preparing to tee it up in the same Byron Nelson Championship as world No.3 and three-time major champion.
Spieth, a student at the Jesuit College Preparatory School, was a standout amateur golfer and had written to tournament organizers hoping for a sponsor's exemption.
Not only was his request granted, but he made the cut and finished tied 16th.
Spieth's golfing resume was already impressive. Among his accolades was the 2009 USGA Junior Amateur title, and he was a former US Junior Ryder Cup player.
But amateur exemptions were rare, particularly for schoolboys, and he crafted the letter carefully with the help of his father and others.
He told of his accomplishments, why he wanted the exemption and why he would be a good person to receive an invite. He talked about attending the tournament as an eight-year-old, and recounted a tale of a close encounter with Phil Mickelson
, one of the game's biggest stars.
"Now I want to create similar memories for other kids who may one day love the game like I do," he wrote.
He also told tournament chief George Conant how his friend Justin Thomas -- now the world No.1 -- had made the cut at the Tour's Wyndham Championship and how another of his junior colleagues, Matteo Manassero, had finished tied 13th at the British Open.
"I remember when I got the call I was in class my junior year at Jesuit," Spieth told reporters ahead of the AT&T Byron Nelson Championship at Trinity Forest in Dallas this week.
"I missed the call but I knew I was going to get a call either way that week and so I went out in the courtyard, it was like the middle of the day in February, sometime in February and I called them back and they said that I was going to get the exemption.
"Needless to say the rest of my day was not very productive and it was very productive at the golf course afterwards. I think I practiced past dark that night. I was obviously very excited."
Spieth went on to the University of Texas before turning pro in 2012. The first of his 11 PGA Tour titles came in 2013 and his last in an epic British Open
at Royal Birkdale last July.
In 2015, at the age of 21, he became the second youngest player to win the Masters after Tiger Woods, and added the US Open title two months later. He became world No.1 for the first time later that year.
Cruising on golfboards
Spieth, who lives in a house formerly owned by fellow Tour star Hunter Mahan in Dallas, is a regular at Trinity Forest and admits he rides golfboards -- like surfboards on wheels -- with music blaring as he plays the course with friends.
"I don't walk when I'm not on Tour so golfboards are great," added Spieth.
"It's good for pace of play and so we typically go out with four, five guys all on golfboards and just cruise around and, you know, in three and a half hours with a five-some and it's a blast.
"It's funny when you get on it for the first time, it's pretty awkward. By the third or fourth hole you get the hang of it."
Thomas, who went to No.1 after last week's Players Championship, and second-ranked Dustin Johnson are absent this week.
So, too, is Woods, who instead announced he will next play at Jack Nicklaus' Memorial Tournament at Muirfield Village, Ohio, starting May 28 -- an event he has won five times.
Spieth will play alongside former US Open champion Graeme McDowell of Northern Ireland and fellow Texan Jimmy Walker, who is back in form with a tied second at the Players after a lengthy struggle with Lyme disease.