A spokesman for Fanatics, which runs the NFL's online store, confirmed to ESPN that, over the past 24 hours, more Villanueva gear, including jerseys and name and number T-shirts, has been ordered than that of any other NFL player.
Villanueva beat out New England Patriots quarterback Tom Brady for the top spot. Philadelphia Eagles quarterback Carson Wentz, Dallas Cowboys quarterback Dak Prescott and Green Bay Packers quarterback Aaron Rodgers rounded out the top five over the past day.
Both the NFL Shop and Fanatics websites had Villanueva jerseys and T-shirts in men's and women's sizes.
A former Army Ranger who earned a Bronze Star and served three tours in Afghanistan, Villanueva was the only Steelers player who came outside the tunnel during Sunday's national anthem, after the team collectively decided not to be on the sideline during the song. Pictures and video of Villanueva standing, with his hand on his heart, filled social media networks.
His actions weren't supported by all, including his own coach. Asked after the Steelers' 23-17 loss to the Chicago Bears what he thought of Villanueva's positioning for the anthem, Mike Tomlin responded, "I was looking for 100 percent participation. We were gonna be respectful of our football team."
While Villanueva, a Spanish-American, already has a strong following in Latin America, it is unprecedented to see an offensive lineman rise to the top of NFL player sales for any period of time. The only comparison of an out-of-nowhere player to see a rise to the top was backup defensive end Devon Still, whose Cincinnati Bengals jersey became one of the league's most popular jerseys in 2014, after his daughter's fight with cancer became public.
"I don't know if the most effective way is to sit down during the national anthem with a country that's providing you freedom, providing you $16 million a year ... when there are black minorities that are dying in Iraq and Afghanistan for less than $20,000 a year," Villanueva told ESPN last year, when San Francisco 49ers quarterback Colin Kaepernick first started kneeling.