All the scouting reports were similar. When the Minnesota Vikings selected Pittsburgh offensive tackle Brian O'Neill with the 62nd overall pick earlier this spring, they knew they were gaining one of the most athletic linemen in the draft whose upside appeared limitless.

His measureables were off the charts: 98th percentile in the 40-yard dash, 98th percentile in the 3-cone drill, 91st percentile in the 20-yard shuttle run. O'Neill's 4.82-second 40 time was the fastest among all offensive linemen at the NFL scouting combine. He even tied the time of (an albeit slow) quarterback Jared Goff of the Rams from two years prior.

As the uncertainty surrounding Minnesota's offensive line mounts throughout the offseason, questions are often raised about the likelihood that the 6-foot-7, 297-pound O'Neill will be ready to take over at right tackle this season if needed.

Everyone from general manager Rick Spielman to coach Mike Zimmer to O'Neill himself has said the same thing: The rookie needs to get stronger if he's going to play tackle in the NFL. Handling speed off the edge has long been one of O'Neill's strong suits. Doing it against elite edge rushers will require greater strength.

Just over a month into his tenure as a Viking, O'Neill is starting to notice his body changing as he gets into an NFL strength, conditioning and nutrition program. O'Neill said he hopes to be around 305 pounds by the end of spring workouts. In the coming months, that number may increase.

It may sound like fun, but adding mass to one's frame in a short amount of time doesn't boil down to a quick fix of binging on pizza and chips every night. Putting on healthy weight while learning an NFL playbook is no cakewalk.

The good news for Minnesota? This isn't O'Neill's first time having to transform his mind and body to meet the demands of playing tackle. And having to do so quickly.

O'Neill hasn't played tackle that long. He excelled as a tight end (33 receptions for 614 yards and eight touchdowns) and as a defensive end (45 tackles, five sacks, three forced fumbles) as a senior in high school. He was rated the fifth-best tight end prospect from his native Delaware when Pitt recruited him.

O'Neill, who weighed 235 pounds when he started college, redshirted in 2014. He moved to tackle before the 2015 season. An offseason injury to former Panthers tackle Jaryd Jones-Smith left Pitt scrambling to find help for their offensive line. O'Neill, a big, blocking tight end who occasionally went out for a pass, was the perfect candidate to fill the void.

Pitt coach Pat Narduzzi had little doubt that O'Neill could seamlessly make the transition. Less than three years before O'Neill would be drafted in the second round, Narduzzi foreshadowed just how far his ceiling would rise by moving inside.

"We talked about how many first-round draft choice tight ends there were compared to offensive tackles and where he had the ability to be a part of that," Narduzzi said. "I think that's something that played into the whole puzzle there."

But this wasn't Narduzzi's decision to make.

"I didn't tell him he had to move to tackle," he said. "Just because a guy got hurt doesn't mean you need to sacrifice everything you've worked for and wanted your entire life. I told him to take a day or two to decide, but if you make that move you have to be all in and want to do it."

Narduzzi's phone rang the next day. O'Neill was ready to make the switch. Time was of the essence.

'See food, eat food'

Six weeks stood between O'Neill and the start of training camp ahead of the 2015 season. Once he decided to change positions, he immediately started to work on changing his body.

From late June until early August 2015, O'Neill went from what he called a "skin and bones" 250 pounds to 285 pounds. Doing so required an immense buy-in from O'Neill at the guiding hand of Pitt head strength and conditioning coach Dave Andrews.

While working at the University of Cincinnati earlier in his career, Andrews aided Jason Kelce's transformation from a 230-pound walk-on linebacker to a 280-pound center by the time he left college. Like O'Neill, the Super Bowl champion Kelce ran the fastest 40-yard dash among all offensive linemen at the combine in 2011.

Andrews had about a month-and-a-half to install a system for O'Neill to gain upwards of 35 pounds so he could hold his anchor on the offensive line. In theory, the plan was simple: There was no set number of calories O'Neill had to consume each day nor specific foods he needed to prioritize over others. All that mattered was that the tackle was putting enough in his body to gain weight. If the scale wasn't moving upwards, he needed to eat more.

"I called it the 'see food diet,'" Andrews said. "He's like, ‘I don't like seafood.' I said, 'No, you're going to see food and eat it.'"

Playing the calorie game became a full-time job for O'Neill that summer. Peanut butter and jelly sandwiches were an important staple in his diet, in which he didn't allow himself to go more than 30 minutes without eating and often set his alarm for a 3 a.m. middle-of-the-night snack.

"It made for some fun 100-degree camp practices in Pittsburgh when you're putting that many calories in your body," O'Neill joked.

Gaining weight might have been the easiest part of his transition. Keeping that weight on with the demands of training camp was difficult.

"It takes an awful lot of discipline," Andrews said. "We did daily and weekly weigh-ins. Body weight is an attitude as well. I'd tell him I want to see him up a pound tomorrow, regardless of whether it was water weight or true fat gain, true muscle gain. At that point, I just wanted to see something change on the scale. You're talking about a 35-pound difference in a six-week period. That's about a pound a day. Not all good weight, but the main emphasis was to get him to a point where he could anchor down at 285."

In gaining a large amount of mass, coaches never saw O'Neill lose his athletic edge. Andrews' plan for the weight room was to put his foot on the pedal and develop as much "absolute strength" as possible. Those six weeks were about helping O'Neill reach the strength needed to play tackle. Refining that strength came later.

"Basically we went into it with nothing to lose," Andrews said. "Any time you have a young man that is gaining weight, it's very easy to get them a little bit stronger. ... I stressed him to the point where we could check metrics by vertical leap just to make sure we weren't overtraining the young man."

To the delight of his coaches, the opposite happened. Possibly the most noteworthy part of his transition can be traced back to one critical measureable.

At 250 pounds, O'Neill reached a 28.5 inch vertical. Some 47 pounds heavier at the combine, he jumped 29.5 inches.

"He is definitely one of the elite guys who you will see test that way," Andrews said. "With a 40- to 50-pound gain, his performance numbers didn't change. That's a testament to what this kid has done, how he's gone about his recovery and how he's gone about preparing."

'Just touching the surface'

Getting through training camp that season was a major hurdle crossed for O'Neill. Then came his biggest test: putting it all together on the field.

"The first couple of games things were flying fast and you can only prepare for so many different looks," O'Neill said. "Once you kind of get an eye for everything conceptually in terms of play structure and why we do things it comes quicker."

O'Neill mastered how to adapt to his new position while managing the changes that came under four different offensive coordinators during his career at Pitt. Going from a pro-set offense to a system that mixed in spread and power concepts provided O'Neill an opportunity to learn a variety of blocking schemes. His athleticism is what makes him such an intriguing addition to the Vikings' outside zone-blocking scheme predicated on movement and the ability of its linemen to get to the second level.

From 2015 to 2017, O'Neill notched 37 starts at tackle. In 817 snaps during his redshirt junior season, he allowed one sack, two QB hits and six hurries. Pro Football Focus gave him a grade of 98.3 in pass-block efficiency, the third highest among draft-eligible tackles.

As the Vikings work toward wrapping up their spring offseason program, O'Neill is fully immersed in his next transition from a college to professional offensive tackle. The physical difference between the rookie and his right tackle counterparts Mike Remmers and Rashod Hill is understandably noticeable. O'Neill aims to stay on the level of his teammates in terms of the knowledge and skill to play the position.

"At offensive tackle that is the biggest difference, if you don't do your job the play is over," he said. "And especially left tackle and even right tackle, protecting the quarterback is the No. 1 priority, at least for an offensive lineman. Being able to do your techniques consistently every time, that's kind of the biggest difference because you might be able to get away with some stuff at tight end. At least I did when I played. At tackle, you're out there on an island."

Whether O'Neill will be ready to step in as a rookie will be determined by how quickly he picks up the playbook and the rate at which his body responds to an intense next few months. Having gone through such an extreme transition three years ago set him up for his current situation. Now it's time to take the next step.

"I think he's just touching the surface," Narduzzi said. "He's still a tight end playing tackle and his best years are ahead of him, for sure."