The IMG coaches envisioned him as an offensive tackle, a blocker who clears lanes for running backs and, more important, protects high-priced quarterbacks. His wingspan alone (35½-inch arms) promised to make him hard to get around. His performance in the tests given to offensive linemen — the 40-yard dash, shuttle runs and various agility drills that measure an athlete’s stamina, balance and ability to change direction — put him in the top ranks of the N.F.L.’s offensive-tackle prospects in recent seasons. His body fat was below 20 percent, exceedingly low for a man his size. “In my years of coaching, I probably haven’t had anybody who looks like that, top to bottom,” Jay Butler, a former N.F.L. strength and conditioning coach who worked with Mailata at IMG, told ESPN.

Offensive tackle, though, is one of the most technically demanding positions in football. It requires size, complicated footwork, a high degree of intelligence and, usually, the acquired wisdom — gained over years of high school and college competition — needed to win the battles against defensive players who come charging across the line of scrimmage. One mistake can cost a team a game — or a season, if the error results in a $30-million-a-year quarterback’s leaving the field on an injury cart.

As Stoutland, who is the Eagles’ offensive line coach, watched Mailata go through drills — mainly simulations of pass blocking and run blocking — his skepticism evaporated. “Right away, I was like, Hello!” he recalls. “You better pay close attention here.” He was standing next to a scout for the Pittsburgh Steelers. “We were both looking at each other, like, Holy cow, what are we seeing here?”

Less than two years later, Jordan Mailata has just begun his second season as an N.F.L. player, following a year in which an ESPN writer named him the Eagles’ “most improved rookie” — a highly unusual honor, considering that he never set foot on the field last year in a regular-season game. But his performance during the 2018 preseason had turned some former offensive linemen into cheerleaders. “Borderline obsessed with this dude at this point. This is crazy,” Ross Tucker, a broadcaster and former N.F.L. lineman, tweeted while also projecting Mailata as a future All-Pro. Mailata had pass-blocked competently and used his strength to clear big corridors for running backs; it was not the man-versus-boys stuff of the rugby video, but for a pure novice, it was impressive. His progress in practices was said to be remarkable (hence the “most improved” accolade). The buzz raised expectations and, if anything, increased the pressure on Mailata. Is he really a future star or just a curiosity piece? How soon until he is trusted to play in a game that counts? More broadly, how much football can you cram into an athlete, even one as big and outlandishly gifted as Mailata, if he has never played the sport before?

The 2018 N.F.L. draft took place in April, less than four months after Mailata arrived in Florida to begin his football education. The Eagles actually made a trade in order to move up in the seventh round and select him before the Steelers could. When his name was called, he walked out onto the stage at AT&T Stadium in Arlington, Tex., wearing a white untucked shirt and a pair of jeans, along with a beige bomber jacket purchased from Johnny Bigg, an Australian men’s wear store that features garments in sizes XL to 9XL. (Many of the top college players dress for the draft in expensive bespoke outfits.) The commentators on the N.F.L. Network went into near hysterics when his name was called. “You’re about to see absolutely no footage of him playing American football,” one said. They showed the rugby video, and when Mailata steamrollered an opponent and sent him staggering backward, another commentator cackled, “Get some, little fella!”