Since then, Matthews has remained in the locker room during the national anthem.
According to ESPN, Matthews responded to fan's question on Twitter by stating that he would "be done playing football" if the NFL were to put in place a rule that would require all players to stand.
Matthews' profile photo on Twitter is of his brother, Christopher Ruiz, a marine who died October 2, 2015 while serving in Afghanistan.
"Let's hope it doesn't get to that", Matthews told the station. Owners are expected to discuss the issue next week.
A former college teammate of Colin Kaepernick, the free agent quarterback who first began protesting injustice by kneeling during the anthem last season, Matthews has also donated $75,000 to less fortunate communities. "I think it's gonna be an uproar if that is to happen because you're basically taking away a constitutional right to freedom of speech".
"The current dispute over the National Anthem is threatening to erode the unifying power of our game, and is now dividing us, and our players, from many fans across the country", Goodell's statement said.
Talk of the possibility of a new rule increased when NFL Commissioner Roger Goodell issued a statement saying, "We believe that everyone should stand for the National Anthem". President Donald Trump had tweeted the day before that players need to stand or be fired.
Goodell also wrote the anthem debate will be a large topic of discussion at league meetings next week in NY. "If you see wrong and don't say anything, that's wrong".