Bruce Maxwell of the Oakland Athletics became the first major league baseball player to kneel during the U.S. national anthem on Saturday, adopting a protest started by former San Francisco 49ers quarterback Colin Kaepernick in response to police treatment of blacks.

More players could follow -- there's been a major backlash by athletes and executives after U.S. President Donald Trump denounced protests by NFL players at a rally on Friday. The Athletics quickly voiced support for Maxwell, tweeting shortly after the anthem that they "respect and support all of our players' constitutional rights and freedom of expression" and "pride ourselves on being inclusive."