Here was a young, talented kid who, at 21 years old, already had the potentially dooming combination of both wealth and status in one of the country's most sports-crazed cities.
But as the tales grew and the scrutiny intensified, Nill thought back to his impressions of Seguin as a teen playing for the Plymouth Whalers -- positive, pleasant memories that seemed at odds with what he'd heard lately.
So, when he decided to trade for Seguin and Rich Peverley in July -- sending Loui Eriksson and three prospects to the Bruins in his first big move as new GM of the Stars -- he did so with confidence that Seguin was not the person, or the player, people had portrayed.
And when he first met with him after the deal was made, his suspicions were quickly confirmed.
"He wanted tapes," Nill said.
Turns out, the first thing Seguin wanted to do after learning his whole world was turned upside down -- after learning the very franchise that had drafted him, the club with which he hoisted the Stanley Cup following his rookie season in 2011, had cut bait and abruptly dealt him -- was get to work.
He wanted tape on Jamie Benn, who a few months later would be named the team's sixth captain since the franchise moved to Dallas in 1993. He wanted to study the technical side to Benn's game, how he played, whom he worked with and why. For a player who was branded with the scarlet "B" for "Bad Boy" in Boston, here he was, eager and earnest to hunker down and do his homework.
"Here is a young man that cares," Nill told ESPN.com. "He didn't like the perceptions he was being pegged with. Like every young man, he's made mistakes, but right from day one he's been professional."
And in the six months since, Seguin has done nothing but reinforce that impression. Instead of running from his past, Seguin told the staff in Dallas he preferred to tackle all of the Boston fallout head-on. He also immediately engaged in charity work with his new team, partnering with the Southwest Wheelchair Athletic Association and sponsoring a suite for victims of severe spinal cord injuries, whom he meets after every home game, win or loss.
"Accountability," Nill said, when asked what about Seguin has stood out most since he's been in Dallas.
That has become an oft-used word in Seguin's lexicon, especially lately. As one of the team's important young leaders, Seguin has had to answer the bell for the team's current slide. Though the Stars (21-18-7) remain in 10th place in an uber-competitive Western Conference -- where they sit only six points back from the eighth-place Minnesota Wild -- they have only just emerged from their toughest skid of the season. Before Tuesday's 5-2 win over Edmonton, in which Seguin snapped a five-game pointless streak, Dallas had dropped a season-high six straight.
It's no coincidence that Seguin's recent drought coincided so neatly with the team's struggles. His role is a different one than in Boston, where he was playing on the third line when they advanced to the Stanley Cup final last spring.
Now, Seguin is an absolutely vital cog to the Stars' 11th-ranked offense. Instead of playing wing, he has moved to center -- his natural position -- on the team's top line with Benn, who also switched back to his natural position on left wing. The results have been encouraging. The tandem has forged an undeniable chemistry on the ice, where they have combined for 37 goals and 81 points. Seguin leads the team with 21 goals and 42 points; Benn, who recently earned a spot on Team Canada's Olympic squad that is headed to Sochi next month, has 16 goals and 39 points.
"Jamie Benn is a great player, but wow, has [Seguin] been good for him," one Western conference scout said recently.
What's even more impressive is that they've produced so much at even strength. Of Seguin's 42 points, only 11 have come on the power play. Of Benn's 39 points, only eight have come on the man-advantage.
"What I've seen from him, I really liked," Stars coach Lindy Ruff said of Seguin. "I thought maybe there would've been some tougher struggles putting him back in the middle, but he handled the defensive stuff pretty well. And then on the offensive side he's been dynamic. He's been a difference-maker most nights, one of the best shots I've seen -- quickest, hardest -- and he's an elite skater."
Seguin's chemistry with Benn, in part, can be attributed to their friendship off the ice. They have been attached at the hip since training camp and live in the same apartment building in Dallas. For all of the talk of Seguin maturing, however, Benn pointed out that he still has not abandoned all vestiges of the bachelor life.
"He can't cook," Benn said. "I don't know how he eats. It's either a steak dinner at my place or Domino's."
The good-natured ribbing between the two is a welcome sign of Seguin's ease in assimilating in Dallas. While Seguin was firmly entrenched in a room full of veterans in Boston, players such as Zdeno Chara, David Krejci, Patrice Bergeron, he has more contemporaries on his current squad, and as such, is more invested in the team's leadership group.
"That's what I'm trying to work towards," Seguin told ESPN.com. "It's the first team I've played on in a long time where there's someone younger than me that I'm playing with."
Perhaps the best indicator of Seguin's maturation is his honesty. Though many of the stories and rumors from Boston may have been overblown, Seguin doesn't deny they exist. He is frank and candid in discussing what appeared to be a bitter divorce with the Bruins organization, and he doesn't hide the fact that it still motivates him.
"What do you think?" he asks with a laugh. "Yeah, any time people talk bad about you, you get more determined. I try to let my play and hockey dictate what I have to say."
Peverley has noticed the positive effects.
"I think he's taken everything that's happened over the course of the past three years and learned from it," Peverley told ESPN.com. "I think it's made him a better hockey player, a better person. You can definitely see it in his game. He's driven this year."
Sure, Seguin still wants to prove the Bruins wrong for giving up on him. After all, how many teams part ways with a player of his potential after just three years? He is learning how to become a professional, and there were bumps along the way, but he was a good player for Boston. He had seven points in 13 playoff games as a rookie, finished with a plus-34 in his second season, and registered 32 points in 48 games during a lockout-shortened 2012-13 season.
Besides, those growing pains are not exclusive to Seguin. Patrick Kane, whom Seguin played with in Switzerland during the lockout, had similar experiences in Chicago during his first few seasons. Kane himself admitted that some of his transgressions were probably worse.
"He's just a regular kid. Things just got magnified in Boston," Peverley said. "I don't think it was fair, to be honest."
Some of that could have been quickly forgotten had the Bruins ended last season with the ultimate prize, instead of falling to the Blackhawks in the Stanley Cup finals.
"If the Bruins won the Stanley Cup, he'd be thought of differently," Nill said. "He took a lot of the heat. He was a guy that got knocked down for those things. For some reason, he became the poster child and I think it was unjust."
If Seguin harbors resentment, he hides it with diplomacy. He still has a soft spot for the city of Boston, he says, and has been back to visit on his own. He still talks to former teammates and people not in hockey circles, friends from clothing stores or barbershops he used to frequent. He still holds many fond memories from his time there -- chief among them the 2011 Stanley Cup championship.
"Boston will always be a part of me," Seguin said.
But it's time to move on, too. And in Dallas, Seguin has.