There's the cozy tie with the head coach.
Their history goes back to the Carolina Panthers, when Sean McDermott was the defensive coordinator and Mike Tolbert was the fullback with granite-like toughness and some serious dance moves.
They were close enough that Tolbert and other members of the Panthers' backfield included McDermott in "The Breakfast Club," which was what the small group of players who would work out in the morning at the team's facility called themselves. McDermott would be right in there with them, bright and early.
But Tolbert's decision to sign with the Buffalo Bills as a free agent Wednesday goes well beyond McDermott calling him to say, "I need you, I want you." It goes beyond the bond of trust built through pumping iron and Tolbert appreciating McDermott's ever-present positive vibe.
Joining the Bills was good for Tolbert's football survival, because he plays a position that has gradually been disappearing from the game. But it's a position that McDermott maintains will be a "big part of this offense." Big enough that, in addition to Tolbert, the Bills also signed free-agent fullback Patrick DiMarco from the Atlanta Falcons.
"This is going on my 10th season, and the fullback has slowly been dying out," Tolbert said during a news conference Friday. "You get a guy like Coach McDermott, who believes in us. He not only brings in myself, but also Patrick DiMarco.
"So it's something that we can help benefit, really bring value to the position, to the team with our versatility, helping out special teams, doing that type of stuff -- the grit and the grunt work."
Tolbert, a former Coastal Carolina standout who spent his first four NFL seasons (2008-11) with the San Diego Chargers and the last five with the Panthers, has established himself as one of the league's best and most versatile fullbacks.
He's known for using his thick, 5-foot-9, 250-pound frame to deliver crushing blocks, and effectively power through piles in short-yardage and goal-line situations. For his career, he has produced 2,402 yards and 33 touchdowns on 630 carries, averaging 3.8 yards per attempt.
Tolbert also has 203 receptions for 1,783 yards -- an average of 8.8 yards per catch -- and 12 touchdowns.
"I like to call myself multi-faceted," he said. "I feel like I can run the ball, I can block, obviously, because I've played fullback at a high level. I'm a great pass-catcher. I can pass protect. I run routes, I play special teams. I do it all."
Tolbert's nickname is the "Tol-dozer." That's what McDermott likes to call him.
As far as how Tolbert is listed on the roster? He doesn't consider himself as having any single designation. He'll leave it to McDermott and offensive coordinator Rick Dennison to determine his role on any given snap.
"I see myself as a football player," Tolbert said. "So if Coach McDermott and Coach Dennison want me to run the ball 10-15 times a game, I'll do it. If they want me to go block into a brick wall head-first on the goal line, so Shady" McCoy "can get in the box, I'll do it.
"It doesn't matter to me. I just want to play football. I love playing ball and I'm doing that in Upstate New York."
McDermott doesn't only see value in Tolbert's physical skills. He views him as a strong leader, someone who is serious about his craft but knows when to lighten things up in the locker room. McDermott made a point of mentioning that Tolbert is a "solid dancer."
"First of all, he’s a family man, a good person," the coach said. "And in order to be a great leader, you’ve got to lead by example and you see that on a daily basis with a man of Mike’s caliber off the field. What he does in the community is phenomenal as well. He’s just got that 'it' that people gravitate towards."
"I'm the product of a single-parent home and I kind of had to make myself jolly to get by sometimes," Tolbert said. "Now, I just exude that on everybody else around me -- the joyful attitude, the light-hearted spirits, the pranking, the joking and playing around. I think it's necessary for a team, because at times, when things are not going your way, you can kind of get down on yourself. You need somebody to kind of poke you in the butt and say, 'Hey, let's go and have a good time.'"
He expects that will be the case for him and his new teammates on fall Sunday afternoons in Orchard Park.
Tolbert remembers how daunting that was as a rookie with the Chargers, during a 23-14 loss to the Bills in 2008. He can only imagine how strongly the support will be now that he's a member of the home team.
"Everybody knows that Buffalo is one of the most football fanatic cities in the country," Tolbert said. "I can remember my rookie year, nine or 10 years ago ... we were playing in Buffalo and the fans were sitting right on your neck. We were just getting screaming and screaming and screaming and I'm just turning around like, 'Man, will you leave me alone?' But it's all part of it.
"The louder the stadium, the better I feel like I play."