Julio Rodriguez was barely 18, playing baseball in the United States for the first time, when he made his biggest impression on a Seattle Mariners franchise that now adores him.

It wasn't how he hit or how he fielded or how he ran — it was how he watched.

Minor league spring training can be long and arduous, with early wake-up times and heavy conditioning before players even pick up a bat or a glove. Rodriguez got his first taste of it in 2019, less than two years after signing out of the Dominican Republic. But he quickly carved out a routine. After his day was finished, he'd walk to the main field of Peoria Sports Complex, stand against a brick wall on the walkway behind home plate and watch the major league spring training game with noticeable intent — backpack on his back, brim of his cap pulled down above his eyes, a budding superstar hiding in plain sight.

Many of those responsible for rewarding Rodriguez with a record contract have harkened back to those moments in recent weeks. To them, that time embodied three defining characteristics that are as pronounced as his five tools — a youthful obsession with baseball, an unconditional devotion to his teammates and a quiet, assertive confidence that is ever-present.

"He's watching because he's fascinated with what's happening with the major league players and because he knows that that's where he's going to be," Mariners president of baseball operations Jerry Dipoto said. "And he's been sizing it up since he was 18 years old."

With less than five weeks left in his rookie season, Rodriguez, now 21, is the best player on a team poised to snap a historic postseason drought, a favorite for the American League Rookie of the Year Award and, as of Friday, owner of a long-term deal that will pay him anywhere between $210 million and $470 million over the life of his career, an unprecedented — and highly complex — contract for someone with less than a full year of major league service time.

The Mariners' principal decision-makers were initially captivated by Rodriguez's ceiling, then awed by how he changed his body to become a dynamic center fielder. They marveled at how he handled torturous early struggles to somehow become an All-Star at midseason and were drawn by how his rise has helped propel the group that surrounds him. But they were also moved by his infectious joy and unwavering authenticity.

They saw it in how his eyes lit up when his name was listed among potential fill-ins at a major league spring training game for the first time and how he went around the room high-fiving everyone on the list with him. In how he traveled to West Virginia to boisterously cheer for teammates at the South Atlantic League All-Star Game, even though an injury had kept him from participating. In how he became a beloved figure within a big league clubhouse full of accomplished veterans who would typically scoff at a young player who promotes himself so aggressively.