Trump has also condemned African-American players in other sports, spurring critics to say his comments are racially charged and meant to stoke his base ahead of the November 6 midterm congressional elections. And in Miami, two Dolphins - Kenny Stills and Albert Wilson - took a knee.
A dozen games were played Thursday night but it was not immediately clear how many saw signs of protest.
In a statement, the NFL said that they continued to discuss the National Anthem with the players and "issues of equality and social justice". Other players remained in the tunnel while the anthem was played.
When former San Francisco quarterback Colin Kaepernick sat during the national anthem of a pre-season game, the NFL struggled to deal with the fallout.
NFL owners pushed through a new policy this offseason which would have punished teams with fines if players demonstrated during the national anthem.
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That combines with the £75m purchase of Virgil van Dijk in January as Liverpool look for their first ever Premier League title. With their signings, Liverpool have strengthened their goalkeeping, midfield and forward options.
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I predict goals in this game for both sides and there is only man who I trust to hit the back of the net. Further, Lehmann had to share his thoughts on Alisson Becker, Liverpool's new number one.
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But there are other clubs who say they haven't got time and wish we hadn't made a decision to do it". The new season gets underway in just two days, with Manchester United hosting Leicester City .
As games opened on Thursday, several players knelt, refused to stand on the field, or raised fists in protest. "I'm grateful he sees what's happening wants to stand up and do something about it as well".
Wilson said he joined the protest because he felt the Dolphins organization gave him the freedom to. Stills was a frequent protestor past year.
The league noted that while players won't be disciplined, it expects all players on the field to stand during the presentation of the flag and the anthem.
But the worst part of Trump's bad tweets is the assertion that players are "unable to define" the reasons for their protest. We had a general conversation about the areas he thinks we could have a real impact on.
However, that policy, announced in May, was put on hold last month when the NFL and the NFL Players Association agreed to suspend enforcement of the new rules.
"But we've seen in other leagues when they've chose to amplify the voices of their players to also emphasize the importance of the issues that we're raising, and change the narrative away from the anthem, that not only is it more acceptable, the fan base gets educated on what we're talking about, and we can actually make some movement".