Major League Baseball can no longer claim to be free of any anthem-protesting players. On Saturday night, A’s catcher Bruce Maxwell took a knee during the national anthem.

Only a day after President Trump criticized athletes who protest the anthem, referring to them as “SOB’s,” and expressing his desire to see NFL owners “fire” them. Maxwell knelt with his hand over his heart, while teammate Mark Canha placed his hand on Maxwell’s shoulder:

Tonight, Oakland A's Bruce Maxwell has become the first MLB player to take a knee during the national anthem. ✊️ 📷: SF Chronicle pic.twitter.com/lElsKjZ7YD — Michael Skolnik (@MichaelSkolnik) September 24, 2017

The timing of Maxwell’s protest is no accident. Earlier on Saturday, he took to Instagram and wrote a vulgar protest in response to Trump’s speech from Friday night. Maxwell posted, “Yeah, f— this guy! Our president speaks of inequality of man because players are protesting the anthem! F— this man! Seriously on the highest platform for our country expressing that it is OK for there to be division of man and rights!”

Shortly after that Maxwell voiced his displeasure again, this time on Twitter:

This now has gone from just a BlackLives Matter topic to just complete inequality of any man or woman that wants to stand for Their rights! — Bruce T Maxwell (@bruu_truu13) September 23, 2017

The A’s released a statement on Twitter supporting Maxwell’s right to express himself:

Until now, the Colin Kaepernick-inspired protests had just occurred within the NFL. Now, with Maxwell’s protest, baseball is dealing with the problem for the first time. Given the disaster the protests have been for the NFL’s popularity one can only imagine MLB isn’t thrilled about this development, especially with baseball’s all-important postseason just around the corner.