This week, he’s using a second shirt.
Per USA Today, Griffin was wearing a plain, short-sleeved gray T-shirt over a long-sleeved white jersey, which presumably has a Nike logo. Griffin has an individual endorsement deal with adidas.
But wearing a shirt with no Nike logo over the shirt with the Nike logo is the same thing as concealing the Nike logo. And it’s likely the league will be talking to Griffin, again.