Kopech, a highly touted right-hander who made his major league debut Tuesday, told the Chicago Sun-Times that the tweets he deleted -- some of which were racist and anti-gay -- do not represent who he is now.
"I had to delete some stuff," he said. "Things I said that were immature and inappropriate. I used some poor language in there. Obviously, I'm trying to be looked at as a role model and the last thing I want to do is have some kid look at what I'm saying and take it the wrong way.
"It's unfortunate that I was ever at that point mentally, but it's not who I am now. Yeah, I cleaned some tweets up and tried to get rid of them. But, obviously, people saw them. It's not who I am now and it's not who I want to be. It was something I did in high school, and with everything I've gone through in pro ball the last five seasons I feel like a big part of my career was maturing. Hate to see it, but it's not who I am anymore."
Kopech, 22, came to the White Sox from Boston in 2016, in the trade that sent Chris Sale to the Red Sox. Kopech was a talented prospect who had been suspended for testing positive for a performance-enhancing substance and broke his hand in a fight with his roommate.
Over two years, he became the White Sox's top pitching prospect and No. 9 in baseball, according to ESPN's Keith Law, hitting over 100 mph on the radar gun. His debut was highly anticipated, with a buzzing crowd on hand at Guaranteed Rate Field on Tuesday. Several rows of fans crowded around the rail above the bullpen to watch Kopech warm up.
His outing was shortened by rain, but Kopech did not disappoint on the mound. He struck out four batters in two shutout innings.
Kopech became the latest baseball player to have to address offensive old tweets. In the past month, Milwaukee Brewers reliever Josh Hader, Atlanta Braves starter Sean Newcomb and Washington Nationals shortstop Trea Turner have all apologized for old tweets that were racist, sexist or anti-gay.
Chicago Cubs ace Jon Lester offered this advice: "If you're on Twitter, please spend the five minutes it takes to scrub your account of anything you wouldn't want plastered next to your face on the front page of a newspaper," he tweeted. "Better yet, don't say stupid things in the first place."