IOWA CITY — On Saturday morning, Brent Metcalf arrived at the site of his grandest glories and believed he would earn the crowning opportunity of his life. He entered the U.S. Olympic wrestling trials as the overwhelming favorite at 65 kilograms. He had lost to one American wrestler over the past three years, and he would be wrestling at Carver-Hawkeye Arena, where he twice became a collegiate national champion at Iowa. He had finished second at the 2012 trials, and after four years, he would realize his aim.

Workers at the arena wore T-shirts emblazoned with a quote attributed to wrestling legend Dan Gable. “Once you’ve wrestled,” it read, “everything else in life is easy.” The trials represent the psychological extreme of Gable’s maxim, and Metcalf understood it too well. There is no safety net for wrestlers, like Metcalf, who not are reigning world champions. One loss, and the chance at the 2016 Rio Summer Games vanishes. Metcalf wrestled one match, six minutes that ended with the score tied. A lifetime of training and four years waiting — poof! — fizzled.

“That’s the sport of wrestling — it’s all or nothing,” Metcalf said. “The looniest guys you’ll talk to in wrestling are really about winning, and all else doesn’t matter.”

Metcalf lost to Frank Molinaro on criteria, tying at 3 but losing because Metcalf scored with three one-point moves and Molinaro registered a two-point takedown. Molinaro used the victory as a springboard to a stunning upset. The ninth seed, Molinaro advanced to the best-two-of-three championship round, where he beat 19-year-old phenom Aaron Pico despite falling in the first match.

Molinaro, 27, is a volunteer assistant coach at Penn State, where he was named all-American four times and won an NCAA championship. He gave up wrestling shortly after college to coach full time. He felt incomplete — “pent up,” he said — without wrestling. One day in 2013, while walking his dog with his wife, he decided he would return to competition, with an eye on qualifying for Rio 2016. He remembers the exact street he stood on in South Plainfield, N.J.

Molinaro entered the trials a significant underdog, and won twice on criteria in the preliminary rounds. He squeaked past Pico, too, winning the final match on criteria with the score tied at four, picking up all of his points with one takedown. After he won, Molinaro fell to his knees and dropped his head to the mat.

“There was just something in my heart that told me I was going to win,” Molinaro said. “I just felt like it was my destiny, and I had no choice but to believe it.”

For Molinaro to stun the tournament, Metcalf needed to stumble. Metcalf also lost a consolation match in which he admitted to giving half-hearted effort. “That one doesn’t mean a whole lot with what we’re after here,” he said later. He was after an Olympic bid. Even a championship Saturday would not have guaranteed it. But Metcalf expected he would earn the chance, in part because, at 29 years old, he had accomplished almost everything else in wrestling.

In high school in Michigan, Metcalf went 228-0. In college at Iowa, he won two NCAA titles and in 2008 earned the Hodge Trophy, given to the nation’s best college wrestler. He finished second at the trials in 2012, the championship dealing him his first loss ever at Carver-Hawkeye Arena. He won championships in the U.S. Open and World Cup the last two years. He was primed.

One mistake, though, could derail everything. In his first match, Metcalf met Molinaro. He seized a late lead, but an aggressive attempt at a takedown allowed Molinaro to score.

“My head is thinking, ‘40 [seconds] to go. Be smart with your hands and feet,’ ” Metcalf said. “And my gut’s saying, ‘Go get another takedown. Score. Stay on his head.’ I’ve got enough experience to know that you’ve got to swallow that pride and swallow that, want to stick a dagger in a guy.”

The loss stung Metcalf and, along with other carnage in the weight class, potentially damaged the U.S.’s hopes. The United States has yet to qualify at 65 kg, and the task will fall to Molinaro, who will now travel to Mongolia for an international qualifying tournament. The top four seeds at the trials — including Spenser Mango, a two-time Olympian who lost in the semis and removed his shoes in the center of the ring, the universal sign for retirement — all lost early.

“The toughest thing for me is letting down my crowd, family, supporters — really, the country,” Metcalf said. “Because I do believe I’m the best guy. Maybe not today. But I do believe I am.”

Not all wrestlers face the all-or-nothing proposition. Kyle Snyder, the Good Counsel alum who last month won the collegiate heavyweight title, will not have to wrestle Sunday until the two-out-of-three championship round of the 97-kg freestyle weight class. He received the automatic bid by virtue of winning a world championship last year at an Olympic weight class, for which he received a ring in a ceremony Saturday night.

Jordan Burroughs (74-kg freestyle) and Adeline Gray (women’s 75 kg) will enjoy the same status Sunday. Rockville’s Helen Maroulis also won a 2015 world title, but her weight class at the world championships was 55 kg, and the Olympics offers 53 kg, so she’ll have to qualify in a challenge tournament.

The United States had qualified for Olympic spots in three of nine weight classes that competed Saturday. Tervel Dlagnev won the 125-kg freestyle, Ben Provisor took the 85-kg Greco-Roman title and Elena Pirozhkova won in the women’s 63-kg class. All three qualified for their second Olympics.

They will move on to Rio. Metcalf has a more difficult task.

“I keep telling people I feel like a 24-year-old,” Metcalf said. “I really do. I got to figure out why the guy who wrestled today wasn’t really the guy who I am.”