The Singaporean became the first person from his country to win Olympic gold when he beat Chad le Clos, Michael Phelps, and Laszlo Cseh to the line in the 100m butterfly in an Olympic Record time of 50.39 seconds.
Cheering him on in Brazil were his high school coach and mentor Lopez, and Texas Longhorns coach Eddie Reese.
However, after graduating from the University of Texas in 2018, he turned professional and returned home to train with the Singapore Swimming Association.
Since that move, Schooling has struggled to achieve the same times he had previously clocked.
World Championships disappointment
Schooling had one of the most disappointing years of his career in 2019.
He was nowhere near his best, and only came home in 54.63 at the national championships in June, before failing to advance out of the heats as one of the 16 fastest in both the 50m and 100m butterfly at the Worlds in July.
That disappointment in Gwangju led Schooling to reconsider his coaching options and think about reuniting with Lopez, he told Singapore's Straits Times.
"Sergio and I go way back. He’s my high school coach and we have always had good camaraderie together, and developed a really good relationship," he said.
After the 24-year-old scraped home to win Southeast Asian Games gold in December, he decided to spend some two and a half weeks with his Spanish mentor in the U.S. – a move that paid off mentally, as Schooling "started thinking a little differently, started to approach practices and hard sets with a more positive attitude".
Now, he will train with Lopez at Virginia Tech until the Tokyo Games.
How to beat Dressel?
With Dressel seemingly miles ahead of himself currently, Schooling has been reflecting on what it will take to beat his American rival in Tokyo.
"I need to be fit enough to swim the 200m fly if I want to do the 100m fly the way I want to," he said, adding that he was "killing it in practice".
And what time is he targeting?
"It’s going to take at least 49-mid to 49-low to win. It is going to take a lot quicker than what I swam in Rio to win."
"I'll be ready for it next year. I've never been one to buy into all the hype."