A credo of the Seattle Seahawks’ fan base is they are known as “The 12th Man.” It’s meant as a rallying cry to implore those on hand at Luman Field for Seahawks home games to be loud at the appropriate times when the situation calls for it.

As far as Adam Thielen is concerned, though, there’s one particular fan at Seahawks home games that takes the idea of being a 12th man a little too literal — to, as Thielen put it, tries his best to get himself involved in the game.

“There’s only one fan that I can think of in my years that really sticks out,” the Pittsburgh Steelers veteran wide receiver said Thursday, “and that’s in Seattle. There’s a guy that kind of stands by the locker room and tries to… get after guys and break them down mentally.”

The subject of unruly fans and dealing with their heckling was of importance this week in the Steelers’ locker room because of the in-game altercation that occurred Sunday at Detroit’s Ford Field.

Steelers receiver DK Metcalf grabbed the shirt collar of a Lions fan as he leaned over the railing behind the Steelers bench, and after a brief interaction Metcalf shoved upward at the fan, who was later identified as Ryan Kennedy from Pinckney Mich.

Metcalf was suspended for two games by the NFL for his actions during the incident.

“I’ve definitely heard more from fans these last few years,” Thielen said. “That’s part of the game. They try to get in your head. They feel like that’s their way to get involved in the game, to try to get in guys’ heads and yell whatever they think they want to yell. Maybe not appropriate, but they do it to try to get in our heads.”

Though Metcalf has not spoken publicly since Sunday — he is banished from the Steelers facility for the duration of his suspension — word via two former NFL players is that Metcalf was set off by foul, offensive language directed at him by Kennedy. Former Steelers linebacker James Harrison said Metcalf told him Kennedy directed a racial slur at him and used another highly derisive term about Metcalf’s mother.

The Lions found no wrongdoing by the fan — who has since hired a law firm and strongly denies the accusations he used slurs — but the NFL said the matter remains under review.

Regardless, several players across the Steelers’ UPMC Rooney Sports Complex headquarters spent Christmas Eve discussing what some say is the trend of an uptick in boorish fan behavior.

“You don’t condone what DK did,” veteran Steelers quarterback Aaron Rodgers said, “but I understand. There have been a lot of crazy comments said my way over the years. The truth is, that would never happen face-to-face. Even people who hate me most, especially in NFC North (where Rodgers played 18 seasons with the Green Bay Packers), it’s been pretty cordial when you see them out and about.

“There are two sides to every story. I support DK. I’ll continue to support DK, and I’m disappointed that happened.”

Longtime Steelers defensive captain Cameron Heyward said it’s not uncommon for players to hear heckling from fans “before, during (and) after” games.

“It’s just part of the game,” he said. “I like it when they are quiet. It means we’re doing our job.

“There are some inappropriate things. As professionals, we have to keep moving beyond that. It’s easier in basketball when you can point a guy out and say get him out of here. Football there is a lot more going on. It shouldn’t be tolerated at all. I respect them as they come watch us play, and they should respect us as we try to put on a good show for them.”

Metcalf is in his first season with the Steelers after spending his first six NFL seasons with the Seahawks. Sunday was his fourth game at Ford Field, and he had reportedly reported Kennedy to Seahawks team security after a prior interaction with him.

Rodgers played nine prior games at Detroit before Sunday. He said he’d had no interactions with Kennedy, who initially identified himself to the Detroit Free Press on Sunday as “Biggest Detroit Lions Fan Ever.”

Rodgers noticed that some videos show that Kennedy raised his arms in apparent joy after his altercation with Metcalf.

“There is a mindset that if you pay for a ticket, you can say whatever the hell you want,” Rodgers said. “I think there should be some code of conduct. Obviously, (Kennedy’s needling) was intentional and there was some celebration afterwards on his part.”

There is a code of conduct for fans. The Lions post it on their website, and presumably every team in the league has it in some form — albeit it very generalized language.

Kennedy told The Free Press that Metcalf was irked because Kennedy was calling him not by “DK” but by his full name: DeKaylin Zecharius Metcalf.

Regardless of the details of this particular incident, as a 21-year NFL veteran Rodgers believes that he has seen the growth of three phenomena that have fueled fan angst: social media, fantasy football and legalized sports gambling.

Each in some way fosters fan anger toward players and/or the ability to deliver that vitriol toward them.

“When I first got in the league, that stuff was more on the fringe,” Rodgers said. “…(It) has brought more eyes to our sport. A lot of that stuff is good for the sport. But at the same time as you start to see parts of society erode, maybe the conduct has changed over the years.

“Now, I’m all for good trash talk. The Browns (the Steelers’ Sunday road opponent) have got ‘The Dawg Pound’ and a great fanbase, (but) there is a line that shouldn’t be crossed.”