Driver has been suspended indefinitely by and Legacy Motor Club due to liking an insensitive meme with a photo of George Floyd's face.
"I am disappointed in myself for my lack of attention and actions on social media," Noah Gragson posted Saturday. "I understand the severity of this situation. I love and appreciate everyone. I try to treat everyone equally no matter who they are. I messed up plain and simple."
Floyd, who was Black, died in 2020 after a white police officer knelt on his neck.
Josh Berry will be in the No. 42 Chevrolet in Sunday's race at Michigan International Speedway to replace Gragson.
NASCAR said Gragson violated the member conduct of its rule book, without providing details.
"His actions do not represent the values of our team," Legacy Motor Club said in a statement.
The 25-year-old Gragson, who is from Las Vegas, is in his first full season in the Cup series and is No. 33 in points.
