Kapler says he won't come out for the anthem until he feels better about the direction of the country.
Kapler claims to be acting after the Robb Elementary School shooting.
Nineteen children and two teachers were killed in Uvalde, Texas.
Colin Kaepernick took a knee during the national anthem in 2016 for a racial justice protest.
Kapler told reporters in Cincinnati, Ohio, that he doesn't expect it to move the needle, but that he feels strongly enough about it to take that step.
He had earlier penned an essay on his website explaining his unhappiness at standing for the national anthem following a minute's silence for the victims before a game on Tuesday.
The National League Manager of the Year said that they didn't stop to think about whether they were free and brave after the event.
My father taught me to stand for the pledge when I believed my country was representing its people well or to protest and stay seated when it wasn't. I don't think it is representing us well right now.
He went on to say that he wanted to drop to his knees.
I knew that thousands of people were using this game to escape the horrors of the world. I knew that thousands more wouldn't understand the gesture and would take it as an insult to the military, to veterans, to themselves.
Kapler said that he was not ok with the state of this country.
I wish I could have shown what my dad taught me when I was dissatisfied with my country. The home of the brave should encourage this.
Golden State Warriors coach Steve Kerr refused to talk about basketball during a news conference and instead delivered an emotional speech condemning gun violence in the US.