Alejandro Villanueva's jersey just became the hottest buy in the NFL.

It's the top seller in the league after the Pittsburgh Steelers offensive tackle broke with his team and walked out of the tunnel for the national anthem.

The Steelers had decided as a group to stay in the locker room. They were one of three teams to sit out the anthem after President Trump said NFL owners should fire players joining the protest. Trump referred to a player who disrespects the flag as a "son of a bitch."

On Monday, Villanueva's No. 78 jersey was outselling big names like Marshawn Lynch and Aaron Rodgers on the NFL Shop. Fanatics, which manages the site, said it was the top seller across all of its sports platforms.

His jersey may have surged in popularity, but Villanueva said during a press conference that his decision to walk out of the tunnel had caused a lot of embarrassment. He said he made his teammates, coaches and the team's owners look bad.

He said head coach Mike Tomlin told the players to come to a unified decision about what they would do during the anthem. Tomlin wanted unity in the response and when the team couldn't come to a decision, they resolved to stay in the locker room.

Villanueva said he only discussed walking to the tunnel with quarterback and captain Ben Roethlisberger and so many of his teammates weren't aware of what he was planning.

"When everybody sees an image of me standing by myself everybody thinks that the team, the Steelers are not behind me and that's absolutely wrong," he said. "It's quite the opposite because they all would have, the entire team would have been out there with me."

Villanueva was a captain and an Army Ranger who served three tours in Afghanistan and received several medals for his service, including the Bronze Star.

Related: NFL: No fines for teams that skipped national anthem

Protests during the national anthem began last year when former 49ers quarterback Colin Kaepernick took a knee to protest the treatment of black Americans, especially by the police.

During the press conference, Villanueva said he doesn't take offense to players kneeling.

"What people don't understand is people who are taking a knee are not saying anything negative about the military. They're not saying anything negative about the flag," Villanueva said.

"They're just trying to protest the fact that there is some injustices in America. And for people that stand up for the national anthem, it doesn't mean that they don't believe in these racial injustices; they're just trying to do the right thing."

Kaepernick's jersey also hit the top spot after he began the protest.

He pledged to donate all the money he made off jersey sales.

According to the agreement between the league and the players union, players get two-thirds of the money from jersey sales. The rest goes to the union, and some of that goes into a pool for all NFL players.